担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Catalysis A General  

The electrochemical CO<inf>2</inf> reduction reaction (eCO<inf>2</inf>RR) is a promising technology for achieving a carbon-neutral society by converting CO<inf>2</inf> into value-added products using renewable energy. This study investigates Ni-coordinated nitrogen-doped carbon (Ni-NC) electrocatalysts for controlling CO and hydrogen selectivity in the eCO<inf>2</inf>RR under acidic conditions. Ni-NCs were synthesized by evaporating and calcining nickel nitrate, 2-methylimidazole, and carbon black precursors. The introduction of Co into Ni-NCs (Ni-Co-NCs) was explored to tune the hydrogen evolution reaction (HER) activity. X-ray absorption fine structure (XAFS) measurements confirmed the Ni-N and Co-N coordination in the synthesized electrocatalysts. Electrochemical tests in a flow cell reactor with an acidic electrolyte revealed that Ni-NCs exhibited CO selectivity over 90 % in the potential range of −1.0 to −1.5 V vs. RHE, whereas Co incorporation in Ni-Co-NCs enabled control over hydrogen selectivity. The CO/H<inf>2</inf> ratio can be adjusted by varying the Ni and Co compositions, making the synthesized electrocatalysts suitable for syngas production via the Fischer-Tropsch process. Long-term stability tests demonstrated the robustness of the Ni-N active sites. Furthermore, the eCO<inf>2</inf>RR overpotential was reduced by increasing the electrolyte pH, which was attributed to the suppression of the competing HER. This study highlights the potential of Ni-NC and Ni-Co-NC electrocatalysts for practical CO<inf>2</inf> conversion applications, such as tandem electrodes and synthetic gas production.

DOI： 10.1016/j.apcata.2025.120502

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

We investigate the electrochemical reduction of carbon dioxide (CO<inf>2</inf>RR) using Cu-M (M = Ni, Pd, Ag, Au, Zn, Cr) binary alloys. Through experimental and theoretical analysis, we explore the structural and electronic properties of these alloys and their impact on CO<inf>2</inf>RR product selectivity. Our findings reveal that the d-band center of Cu-M alloys serves as a crucial descriptor, influencing product distribution. As the d-band center increases, more CO is produced, while the formation of C<inf>2</inf>products (ethylene and ethanol) follows a volcano-like trend. We also observe a linear scaling relationship between the d-band center and ethylene/ethanol selectivity, providing opportunities for fine-tuning product selectivity. The observation is explained by theoretical calculations that suggest that the d-band center effectively changes the relative binding of *CCH vs *CHCHOH, thereby controlling product selectivity into ethylene vs ethanol formation. We also find that this d-band center dependence is what makes the *CCH vs *CHCHOH adsorption energy, when properly corrected for alloy composition-dependencies, the most reliable theoretically accessible descriptor for ethylene/ethanol selectivity, while the *O adsorption energy does not show a clear correlation with experimental results. This study enhances our understanding of CO<inf>2</inf>RR catalysis and offers guidelines for designing Cu-based alloy electrocatalysts with improved activity and selectivity for sustainable CO<inf>2</inf>conversion.

DOI： 10.1021/jacs.5c14093

Web of Science

Scopus

PubMed

researchmap

掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Catalysis B: Environmental  

In the CO2 electrocatalytic reduction reaction (CO2RR) technology, high CO2 conversion rate is highly required for efficient CO2 utilization from the CO2 resource. In this study, we propose the strategy of combining UiO-66 metal organic framework (MOF) structure with Bi electrocatalyst for highly active CO2RR with selective formic acid production. The synthesized Bi/UiO-66 catalyst shows superior CO2 reduction property, 4.6 times higher current density at −0.7 V vs. reversible hydrogen electrode (RHE) than bare Bi without UiO-66 despite of low electrochemical surface area. Also, NH2 functionalized UiO-66 shows almost no effect on CO2RR as compared to without NH2 probably due to disassembled linkers during CO2RR. Various characterizations such as Fourier transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) indicate carbonate species captured form of CO2 at Zr-MOF site should contribute the high CO2 conversion rate. Our findings demonstrate the feasibility of Zr-MOF as a Supporting material to achieve efficient CO2 reduction.

DOI： 10.1016/j.apcatb.2023.122400

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In the CO2 electrocatalytic reduction reaction (CO2RR) technology, high CO2 conversion rate is highly required for efficient CO2 utilization from the CO2 resource. In this study, we propose the strategy of combining UiO-66 metal organic framework (MOF) structure with Bi electrocatalyst for highly active CO2RR with selective formic acid production. The synthesized Bi/UiO-66 catalyst shows superior CO2 reduction property, 4.6 times higher current density at −0.7 V vs. reversible hydrogen electrode (RHE) than bare Bi without UiO-66 despite of low electrochemical surface area. Also, NH2 functionalized UiO-66 shows almost no effect on CO2RR as compared to without NH2 probably due to disassembled linkers during CO2RR. Various characterizations such as Fourier transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) indicate carbonate species captured form of CO2 at Zr-MOF site should contribute the high CO2 conversion rate. Our findings demonstrate the feasibility of Zr-MOF as a Supporting material to achieve efficient CO2 reduction.

リポジトリ公開URL： https://hdl.handle.net/2324/7172333

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/d0ta08564b

記述言語：英語   出版者・発行元：Solid State Ionics  

Fluoride ion battery is now expecting as a high energy density rechargeable battery which is alternative to Li ion rechargeable battery. For realizing all solid-state concept, fast fluoride ion conductor with wide electrochemical windows is required. In this study, fluoride ion conductivity in doped ASn<inf>2</inf>F<inf>5</inf> (A = Na, K, Rb, Cs) were measured and it was found that reasonably high fluoride ion conductivity was achieved on Rb<inf>0.9</inf>Li<inf>0.1</inf>Sn<inf>2</inf>F<inf>5</inf> which is layered structure and contained intrinsic fluoride vacancy. Transport number of fluoride ion in this Rb<inf>0.9</inf>Li<inf>0.1</inf>Sn<inf>2</inf>F<inf>5</inf> was also measured with fluoride concentration cell, Pb/sample/BiF<inf>3</inf> and the estimated transport number of fluoride ion was higher than 90% of theoretical one. For further analysis of fluoride ion conductivity in Rb<inf>0.9</inf>Li<inf>0.1</inf>Sn<inf>2</inf>F<inf>5</inf>, electrochemical pumping of fluoride ion was measured on the symmetrical cell consisting of BiF<inf>3</inf>/BiF<inf>3</inf> over 48 h and the amount of fluoride transported was reasonably agreed with the coulomb number through the sample. Linear scan voltammetry (LSV) shows the electrochemical stability windows of Rb<inf>0.9</inf>Li<inf>0.1</inf>Sn<inf>2</inf>F<inf>5</inf> was close to ca.3 V.

DOI： 10.1016/j.ssi.2026.117151

Web of Science

Scopus

記述言語：英語   出版者・発行元：Journal of Applied Microbiology  

Abstract Ammonia (NH₃) is a critical molecule for agriculture, industry, and emerging energy applications. However, current industrial production by the Haber–Bosch process is energy-intensive and environmentally damaging, accounting for a significant portion of global CO₂ emissions. In contrast, biological nitrogen fixation (BNF) offers a sustainable alternative by converting atmospheric nitrogen (N₂) into NH₃ under ambient conditions through the action of nitrogenase enzymes. Among diazotrophic microorganisms, Azotobacter vinelandii stands out due to its ability to fix nitrogen aerobically, supported by unique physiological and genetic adaptations that protect its oxygen-sensitive nitrogenase. This review presents a comprehensive overview of NH₃ synthesis with A. vinelandii, highlighting its biochemical mechanisms, nitrogenase structure and function, and the protective strategies that enable aerobic nitrogen fixation. We further examine the diversity and advantages of Azotobacter strains, with a focus on A. vinelandii’s potential for engineered NH₃ production through synthetic biology, metabolic engineering, and emerging bio-based technologies such as photobiocatalysis and bioelectrochemistry. Recent innovations aimed at improving nitrogenase expression, cellular stability, and overall system efficiency are discussed in the context of advancing A. vinelandii as a robust chassis for industrially scalable, carbon-neutral NH₃ synthesis. The review emphasizes the importance of free-living nitrogen fixers in addressing the challenges of sustainable NH₃ production and provides insights into future directions for research and application.

DOI： 10.1093/jambio/lxag083

Web of Science

Scopus

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Biocatalysis and Biotransformation  

Effects of gaseous CO<inf>2</inf> on photocatalytic H<inf>2</inf> formation by water splitting was studied for increasing activity of biocatalyst which was Escherichia coli (E. coli) expressing [FeFe]-hydrogenase. It was found that photobiocatalytic reaction under gaseous CO<inf>2</inf> atmosphere, H<inf>2</inf> formation rate increased by 283% at 60 min, and the amount of H<inf>2</inf> formation increased by 105% at 300 min compared to under Ar atmosphere. This positive effect of gaseous CO<inf>2</inf> was not simply explained by pH effects but assigned to the increased permeation rate of methyl viologen (MV²⁺), redox mediator, through cell membrane of E. coli. CO<inf>2</inf> may be dissolved in cell membrane of E. coli and increased permeability of MV²⁺ resulting in increased formation rate of H<inf>2</inf> by photobiocatalytic water splitting.

DOI： 10.1080/10242422.2026.2619122

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACS Nano  

The development of monolayer hole-selective contacts has proven to be an effective strategy for enhancing the performance and scalability of inverted perovskite solar cells (PSCs). However, current monolayer molecules often suffer from limited charge separation and extraction capabilities due to their small π-conjugated domains, localized carrier orbitals, and weak interfacial binding with substrates. Here, we report a molecular design featuring a double donor–acceptor (D–A) conjugated architecture with an enhanced push–pull effect, spatially separated carrier orbitals for efficient hole extraction and electron blocking, bifacial anchoring for strong binding to both metal oxide substrates and perovskite layers, and a twisted π-skeleton that suppresses self-aggregation and ensures homogeneous monolayer distribution. By replacing conventional [2-(9H-carbazol-9yl)ethyl]phosphonic acid (2PACz) with this double D–A-type monolayer, the PCE improves from 23.69% to 25.61% (certified 25.11%) in small-area PSCs, while large-area perovskite modules (active area of 10.04 cm²) achieve a high PCE of 21.40%. Notably, the devices exhibit excellent operational stability under continuous illumination (100 mW cm^–2) at an elevated temperature (85 °C), maintaining 84.9% of the initial efficiency after 1000 h.

DOI： 10.1021/acsnano.5c21709

Web of Science

Scopus

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACS Applied Nano Materials  

The electrochemical reduction of CO<inf>2</inf> (CO<inf>2</inf>RR) into hydrocarbons has emerged as a promising strategy for sustainable energy conversion and carbon neutrality. Among the various possible products, CH<inf>4</inf> is of particular interest because it can be directly used in existing infrastructure, unlike H<inf>2</inf> and NH<inf>3</inf>. However, despite intensive studies, the intrinsic role of Cu catalyst size in CH<inf>4</inf> selectivity has remained unclear due to the complex interplay between particle size, morphology, exposed crystal planes, oxidation states, and defect structures. In this work, we aimed to clarify the size effect in the CH<inf>4</inf>-selective CO<inf>2</inf>RR by preparing single-layer Cu nanosheets (SLCs). By electrostatically adsorbing Cu²⁺ ions onto titanate nanosheets followed by electrochemical reduction, SLCs with an atomic thickness were synthesized, and their lateral dimensions were tuned by adjusting Cu²⁺ loading. Structural characterization confirmed that SLCs maintained single atomic layers of 0.3 nm at Cu²⁺ loadings of 1.6–7.6 wt %, whereas larger loadings resulted in multilayer Cu (MLCs) at loadings of 7.6–11.7 wt %. CH<inf>4</inf> Faradaic efficiency showed a volcano-type dependence on SLC diameter, peaking at 39%. In contrast, H<inf>2</inf> selectivity followed an inverse volcano trend. Mechanistic analysis revealed that CH<inf>4</inf> selectivity correlates with the fraction of in-plane Cu atoms, whereas H<inf>2</inf> selectivity correlates with the edge Cu atoms. These findings establish the intrinsic size–selectivity relationship in two-dimensional Cu catalysts and provide a strategy for designing oxide-supported single-layer catalysts to optimize CH<inf>4</inf> production in the CO<inf>2</inf>RR.

DOI： 10.1021/acsanm.5c05147

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nature Communications  

Self-assembled molecules are widely used as bottom interfacial layers in inverted perovskite solar cells, yet their application to perovskite top surfaces remains poorly understood. Here, we develop two self-assembled molecules for perovskite surface modification and interfacial optimization with the hole transport layer. Through solvent engineering, ordered and uniform molecular packing is achieved on the perovskite surface. These molecules optimize surface energetics and promote efficient hole transfer when coupled with a homologous hole transport layer. Their large molecular dipoles tune interfacial energy alignment and reduce energetic offsets, thereby accelerating charge extraction from the perovskite layer. This dipole-driven interfacial modulation is effective in both normal and inverted device architectures. As a result, a power conversion efficiency of 26.18% (certified 26.23%) is achieved in normal-structure devices, together with improved operational stability under maximum power point tracking. This work establishes a viable strategy for perovskite surface engineering using self-assembled molecules.

DOI： 10.1038/s41467-026-69198-2

Web of Science

Scopus

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Materials Chemistry A  

The photocatalytic activity of melamine, melem, and melem-phthalimide condensed molecules for hydrogen peroxide generation under visible light in the presence of ethanol as a sacrificial material was investigated. The catalytic activity tests were performed under heterogeneous conditions. Upon irradiation with visible light, melem-phthalimide condensed molecules produced 939 µM hydrogen peroxide, while melem produced 509 µM hydrogen peroxide. The melem-phthalimide condensed molecules were stable in repeated tests, which was confirmed by solid-state nuclear magnetic resonance. Furthermore, the reaction taking place on the surface of the melem-phthalimide condensed catalyst was revealed by electron spin resonance, X-ray photoelectron spectroscopy, and Raman spectroscopy. The reaction mechanism was confirmed by photoluminescence decay spectroscopy and transient absorption spectroscopy. This study revealed that the extended donor–acceptor type heptazine structure significantly contributes to the improved activity through charge separation at the molecular level.

DOI： 10.1039/d5ta06698k

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Catalysis A General  

Effects of cation-doping to InGaO<inf>3</inf> on photocatalytic water splitting activity were studied using a solid-state reaction. Among various dopants, it was found that Mg^2 +which is a lower-valence cation was effective in significantly increased the photocatalytic water splitting activity. NiO-loaded InGa<inf>0.95</inf>(Mg)<inf>0.05</inf>O<inf>3</inf> exhibited the highest hydrogen and oxygen evolution rates, 760 and 342 µmol g⁻¹h⁻¹, respectively. Notably, Brunauer–Emmett–Teller (BET) surface area and bandgap estimated by UV–visible diffuse reflectance (UV–vis DR) spectra were not significantly changed between InGaO<inf>3</inf> and InGa<inf>0.95</inf>(Mg)<inf>0.05</inf>O<inf>3</inf>. Photoluminescence (PL) and PL decay spectra confirmed that 5 at% Mg doping effectively suppressed the charge recombination, indicating improved carrier separation. X-ray photoelectron spectroscopy (XPS) revealed the formation of oxygen vacancy, which compensated the charge neutrality and reduced the free electron concentration. Ultraviolet photoelectron spectroscopy (UPS) confirmed that Mg doping lowered the valence band edge of InGaO<inf>3</inf> and effectively expanded the driving force for the oxygen evolution reaction, although the conduction band was almost unchanged.

DOI： 10.1016/j.apcata.2025.120649

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Energy Storage Materials  

High-voltage sodium dual-ion batteries (SDIBs) are important from resource, energy, and cost, and for this SDIBs, electrolytes with wide electrochemical stability windows and balanced ion transport properties are strongly required. Here, we present the first time application of a highly concentrated sodium bis(fluorosulfonyl)imide (NaFSI) electrolyte in ethyl mesylate (EM) as the non-aqueous solvent. EM shows high stability to oxidation and achieved stable charge and discharge at potential higher than 5 V vs. Na/Na⁺, and SDIBs using EM-based electrolytes exhibited the superior capacity (111 mAh/g) and retention (98.2% after 600 cycles) and extended cycle life compared to the conventional carbonate systems. NMR and Raman spectroscopy revealed that EM strongly solvates Na⁺ ions even at high concentrations, suppressing excessive ion association and resulting in nearly ideal cation and anion transference numbers. The combination of high balanced cation and anion conductivity, along with robust electrochemical stability, provides a new design strategy for dual-ion battery electrolytes. These findings underscore the potential of highly concentrated sulfonate-based electrolytes for high-voltage SDIBs for the next generation, and offer fundamental insights into the relationship between solvent structure, ion solvation, and transport properties.

DOI： 10.1016/j.ensm.2025.104832

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACS Nano  

Photoelectrochemical (PEC) catalysis is a promising approach for converting solar energy into chemical fuels, but a fundamental challenge lies in balancing catalytic activity with efficient light absorption. Catalyst surface coverage on light-harvesting supports often leads to a trade-off that limits overall performance. To address this issue, we developed a high-aspect-ratio (&gt;20) gold (Au) nanopatterned catalyst designed to maximize both light harvesting and catalytic efficiency. Compared to conventional film-type catalysts, the nanopatterned catalyst exhibits a 3.6-fold increase in electrochemical surface area and a 2.5-fold improvement in transparency, enabling greater light transmission to the photoabsorber. In the reduction of CO<inf>2</inf>to syngas (H<inf>2</inf>:CO = 1:1), the nanopatterned catalyst achieves a 240 mV lower onset potential and a 6.2-fold increase in syngas formation rates compared to its film counterpart. These enhancements are attributed to the unique structure of the nanopatterns, which feature smaller grain sizes, higher surface area, and improved light transmittance. This versatile nanopatterning approach is not limited to Au but can be extended to other catalytic materials, including metals, metal oxides, and transition metal dichalcogenides. The design offers a scalable solution to improve PEC performance for a wide range of applications, from CO<inf>2</inf>reduction to other catalytic processes. By overcoming the trade-offs associated with traditional catalysts, this study provides a pathway toward more efficient and sustainable PEC systems.

DOI： 10.1021/acsnano.5c08137

Web of Science

Scopus

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Chinese Chemical Society  

Photocatalysis is an effective method for efficiently using solar energy and producing hydrogen through water splitting. In this study, we investigated an anchor group, chosen from carboxy, pyridyl, and tetrazole moieties, that easily attracts electrons from boron dipyrromethene (BODIPY) and injects them into titanium oxide (TiO₂) to synthesize a new dye-sensitized material for photocatalytic hydrogen production. Target BODIPY sensitizers were synthesized to yield 12%–29% with BODIPY-2-carbaldehyde and corresponding acetonitrile derivatives treated by piperidine or triethylamine as the catalyst. The coordination of the sensitizers onto TiO₂ was examined through attenuated total reflection Fourier transform infrared spectroscopy. The energy potential of BODIPY sensitizers with respect to TiO₂ was analyzed using cyclic voltammetry and differential voltammetry. The molecular orbitals of the BODIPY sensitizers were analyzed using density functional theory. Visible-light-driven photocatalysis with ascorbic acid as the sacrificial electron donor demonstrated hydrogen production. The photocurrent test showed that photo-induced electrons were injected into TiO₂ under visible light irradiation which supported dye-sensitized photocatalytic hydrogen production. The absorption spectra after the photocatalytic reaction showed no change in the pyridyl anchor group system, which suggested that the pyridyl-anchored dye-sensitized photocatalyst showed a good hydrogen production rate and stability.

DOI： 10.1002/jccs.70098

Web of Science

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Solar Energy  

The buried interface in perovskite solar cells (PSCs) is pivotal in influencing the quality of the perovskite films and the efficiency of charge extraction and transport. Recent studies have highlighted the potential of alkali metal ion-based materials for modifying this interface. In this work, we present the first systematic investigation of the effects of different alkali metal hydroxide treatments at the buried interface between the SnO<inf>2</inf> electron transport layer and the perovskite light absorber layer. Our findings demonstrate that KOH treatment significantly enhances the power conversion efficiency (PCE), while CsOH treatment improves operational durability. To achieve a balance between efficiency and durability, we developed a dual alkali metal hydroxide treatment strategy. Notably, the sequence of hydroxide deposition was found to be critical. A KOH treatment followed by CsOH increased the efficiency of mixed cation-based PSCs from 18.46% to 20.31% and improved durability, allowing the device to retain 95% of its initial efficiency after 500 h of continuous illumination at room temperature. Furthermore, this dual treatment enhanced the PCE of formamidinium lead iodide-based PSCs from 21.31% to 21.68%, along with improved operational stability. This study introduces a straightforward yet highly effective method for buried interface modification, offering a versatile approach to simultaneously boost efficiency and durability in a wide range of PSC architectures.

DOI： 10.1016/j.solener.2025.113444

Web of Science

Scopus

researchmap

掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Materials Chemistry A  

Oxide perovskites, such as SrCoO<inf>3</inf>, are considered to be promising air electrode catalysts for solid oxide cells. SrCoO<inf>3</inf> is composed of non-precious elements and possesses catalytic activity for various reactions, including an oxygen reduction and an oxygen evolution reaction. However, the catalytic activity of this material is typically limited at reduced temperatures. In this study, the catalytic activity of SrCoO<inf>3</inf> was improved by co-doping of cerium (Ce) and samarium (Sm) at the A site (Sr site) of SrCoO<inf>3</inf>. Although Ce was considered the B-site dopant in terms of ionic size and coordination number, a small amount of Ce was successfully substituted at the Sr site, simultaneously with Sm. Oxygen reduction and evolution activity were significantly increased by substitution of a small amount of cerium (∼2.5 mol%) at the A-site. At 973 K, the maximum power density generated from the LaGaO<inf>3</inf>-supported cell with Ce-Sm co-doped SrCoO<inf>3</inf> as an air electrode was 0.62 W cm⁻² in fuel cell mode, and the current density in steam electrolysis mode at 1.5 V was 0.93 A cm⁻². The increased air electrode activity could be assigned to the improvement in the surface active sites and electrical conductivity of SrCoO<inf>3</inf> by simultaneous substitution of Ce with Sm at the A site.

DOI： 10.1039/d4ta08181a

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Angewandte Chemie International Edition  

Stable neutral metal radicaloid complexes have been synthesized from a modified tetrapyrrolic pigment, bilatriene, with iridium(I) and rhodium(I) cyclooctadiene (COD) synthons. The bilatriene skeleton contains α-linked conjugated pyrrole units, whereas an N-confused analogue used in this work possesses β-linked pyrrole moieties at the terminal, demonstrating a unique metal binding capability. Unprecedentedly, the metal-COD cations are accommodated at the outer nitrogen sites, which induced the formation of open-shell metal-radicaloid species. The resulting compounds are highly stable under ambient conditions and demonstrated facile redox conversion to afford the corresponding cation and anion species. Furthermore, the radicaloid complexes showed a distinct second near-infrared absorption (NIR-II) capability extending up to 1500 nm along with high photostability. These features emphasized that the complexes can be potential NIR-II light-responsible photothermal and photoacoustic imaging contrast agents based on the metal-radicaloid dye platform.

DOI： 10.1002/anie.202418751

Web of Science

Scopus

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Solar Rrl  

Thermal stress significantly impacts the durability of perovskite solar cells (PSCs), as evidenced by severe degradation observed at 85 °C in this study. This degradation is attributed to gold migration through the soft 2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-MeOTAD) hole transport layer (HTL) into the perovskite layer, driven by gold's low formation energy and diffusion barrier. To mitigate this issue, several vacuum-evaporable hard transition metal oxides as charge extraction interlayers between the gold electrode and the HTL to suppress gold migration are investigated. PSCs incorporating MoO<inf>3</inf>, V<inf>2</inf>O<inf>5</inf>, MoO<inf>2</inf>, and ReO<inf>3</inf> interlayers achieve a power conversion efficiency of ≈20%, comparable to PSCs without interlayers. Notably, these interlayer-equipped PSCs exhibit enhanced thermal durability at 85 °C by effectively suppressing gold migration into the perovskite layer under elevated temperatures, with the MoO<inf>2</inf> interlayer also improving durability at 25 °C. These findings offer a promising strategy for fabricating thermally durable PSCs, contributing to the future commercialization of photovoltaic technology.

DOI： 10.1002/solr.202400705

Web of Science

Scopus

出版者・発行元：Journal of Materials Chemistry A  

Metal-supported protonic ceramic fuel cells (PCFCs) are highly attractive due to their high efficiency, reliability, and low cost. However, until now, there are limited reports on metal-supported PCFCs. In this study, a selective reduction method was used for preparing the metal-supported BaZr<inf>0.44</inf>Ce<inf>0.36</inf>Y<inf>0.2</inf>O<inf>3</inf> (BZCY) cell. It was found that insertion of an La<inf>1−x</inf>Sr<inf>x</inf>ScO<inf>3</inf> (LSSc, x = 0.1-0.25) cathode functional film (CFL) was highly effective for decreasing cathodic overvoltage and ohmic loss, leading to significant increase in power density. Among the examined compositions, La<inf>0.85</inf>Sr<inf>0.15</inf>ScO<inf>3</inf> was identified as the optimal composition of the CFL. With this configuration, an open circuit voltage (OCV) of 1.15 V and a maximum power density (MPD) of 233 mW cm⁻² were achieved at 773 K. Impedance analysis suggests that the increased power density can be attributed to the decreased overvoltage and ohmic loss in the cathode side, due to significantly increased proton conductivity in the LSSc film. This improvement is likely the result of the high concentration of H⁺ in the LSSc film, as indicated by thermogravimetric (TG) and Hall effect measurement. Another challenge in PCFCs is the leakage current at higher oxygen partial pressure. However, the LSSc CFL also effectively prevented H⁺ crossover, resulting in the OCV being almost the same as the theoretical value. Achieving near-theoretical OCV is crucial for the high energy conversion efficiency of PCFCs.

DOI： 10.1039/d4ta06783e

Web of Science

Scopus

記述言語：英語   出版者・発行元：Advanced Materials  

Exploiting the self-assembled molecules (SAMs) as hole-selective contacts has been an effective strategy to improve the efficiency and long-term stability of perovskite solar cells (PSCs). Currently, research works are focusing on constructing SAMs on metal oxide surfaces in p-i-n PSCs, but realizing a stable and dense SAM contact on halide perovskite surfaces in n-i-p PSCs is still challenging. In this work, the hole-selective molecule for n-i-p device is developed featuring a terephthalic methylammonium core structure that possesses double-site anchoring ability and a matching diameter (6.36 Å) with the lattice constant of formamidinium lead iodide (FAPbI<inf>3</inf>) perovskite (6.33 Å), which facilitates an ordered and full-coverage SAM atop FAPbI<inf>3</inf> perovskite. Moreover, theoretical calculations and experimental results indicate that compared to the frequently used acid or ester anchoring groups, this ionic anchoring group with a dipolar charge distribution has much larger adsorption energy on both organic halide terminated and lead halide terminated surfaces, resulting in synergistic improvement of carrier extraction and defect passivation ability. Benefiting from these merits, the efficiency of PSCs is increased from 21.68% to 24.22%. The long-term operational stability under white LED illumination (100 mW cm⁻²) and at a high temperature of 85 °C is also much improved.

DOI： 10.1002/adma.202414576

Web of Science

Scopus

PubMed

掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

Stable neutral metal radicaloid complexes have been synthesized from a modified tetrapyrrolic pigment, bilatriene, with iridium(I) and rhodium(I) cyclooctadiene (COD) synthons. The bilatriene skeleton contains α‐linked conjugated pyrrole units, whereas an N‐confused analogue used in this work possesses β‐linked pyrrole moieties at the terminal, demonstrating a unique metal binding capability. Unprecedentedly, the metal‐COD cations are accommodated at the outer nitrogen sites, which induced the formation of open‐shell metal‐radicaloid species. The resulting compounds are highly stable under ambient conditions and demonstrated facile redox conversion to afford the corresponding cation and anion species. Furthermore, the radicaloid complexes showed a distinct second near‐infrared absorption (NIR‐II) capability extending up to 1500 nm along with high photostability. These features emphasized that the complexes can be potential NIR‐II light‐responsible photothermal and photoacoustic imaging contrast agents based on the metal‐radicaloid dye platform.

DOI： 10.1002/ange.202418751

researchmap

記述言語：英語   出版者・発行元：Royal Society of Chemistry  

Self-repairing catalysts are useful for achieving alkaline water electrolyzers with long lifetimes under intermittent operation. However, rational methodologies for designing self-repairing catalysts have not yet been established. Herein, hybrid cobalt hydroxide nanosheets (Co-ns), with a high deposition (repairing) rate, and β-FeOOH nanorods (Fe-nr), with high oxygen evolution reaction (OER) ability, are electrostatically self-assembled into composite catalysts. This strategy is developed to integrate multifunctionality in self-repairing catalysts. Positively charged Co-ns and negatively charged Fe-nr form uniform composites when dispersed in an electrolyte. These composites are electrochemically deposited on a nickel electrode by electrolysis at 800 mA cm−2. Co-ns form a conductive mesoporous assembly of CoOOH nanosheets as a support. Fe-nr are then distributed on the CoOOH nanosheets as active sites for the OER. Because of the high deposition rate of Co-ns, the amount of Fe-nr deposited increases 22 times compared to when Fe-nr is deposited alone, and the OER current density increases 14 times compared to that of Co-ns alone. The composite self-repair catalyst shows the highest activity and durability under an accelerated durability test (ADT), and its degradation rate decreases from 84 μV cycle−1 (Fe-nr only) to 60 μV cycle−1 (composite catalyst) under ADT conditions without repair.

CiNii Research

出版者・発行元：Journal of the Electrochemical Society  

Solid oxide electrolysis cells (SOECs) are an important subject for storage of renewable energy such as solar or wind power. In this study, tubular type SOECs using La<inf>0.8</inf>Sr<inf>0.2</inf>Ga<inf>0.8</inf>Mg<inf>0.2</inf>O<inf>3</inf> (LSGM) electrolyte film were prepared on NiO-Y<inf>2</inf>O<inf>3</inf> stabilized ZrO<inf>2</inf> (YSZ) with different porosity and it was found that the porosity of the Ni-YSZ tubular substrate is an important parameter for achieving initial high current density and also low rate of durability by preventing the pulse potential noise. The addition of cornstarch as pore-formers was effective for increasing channel size (3.9 μm of average radius) in Ni-YSZ substrate and when 15 wt% cornstarch was added for extruding NiO-YSZ substrate, the tubular cell exhibited the superior initial performance, 0.69 A cm⁻² at 1.6 V in SOEC mode at 873 K. This cell also shows smaller degradation rate by suppression of the pulse potential noise and the high coulomb efficiency of H<inf>2</inf> formation. Increase in porosity of Ni-YSZ substrate is highly important for increasing the initial performance and long-term stability of SOEC.

DOI： 10.1149/1945-7111/ad9d7c

Web of Science

Scopus

出版者・発行元：Catalysis Science and Technology  

Boron nitride has received much attention as an emerging heterogeneous catalyst. Porous boron nitride catalysts were synthesized using boric acid (B) and urea (U) at different molar ratios via a pyrolysis method and applied for cycloaddition of CO<inf>2</inf> to epoxides as metal-free catalysts. The synthesized boron nitride samples had a turbostratic structure, and their porous properties, such as surface area, pore size distribution, and pore volume, largely depended on the molar ratio of B : U precursors. The sample synthesized at a molar ratio of B : U = 1 : 5 with the highest pore volumes among the samples prepared from boric acid and urea exhibited the highest activity for cycloaddition of CO<inf>2</inf> to epoxides, epichlorohydrin and styrene oxide in the presence of tetrabutylammonium bromide (TBAB). There was a good correlation between the corresponding carbonate yield and the pore properties of the catalyst. The addition of melamine (M) during the synthesis greatly developed the porous structure, exceeding 1000 m² g⁻¹ surface area. The sample synthesized at a molar ratio of B : M : U = 1 : 1 : 5 having a large surface area of 1380 m² g⁻¹ with a high pore volume of 1.8 mL g⁻¹ afforded a remarkable yield of 96% for the reaction of epichlorohydrin. The catalyst could be reused at least three times without a significant loss of activity. A cooperative reaction mechanism was proposed in which the hydroxyl groups of porous boron nitride catalysts as weak Brønsted acid sites polarize the oxygen atom of the epoxide, and the bromide ions of TBAB as Lewis base sites activate the carbon atom of the epoxide by the nucleophilic attack.

DOI： 10.1039/d4cy01080a

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemistryopen  

Formic acid is considered a promising hydrogen carrier. Biomass-derived formic acid can be obtained by oxidative decomposition of sugars. This study explored the production of formic acid from cellobiose, a disaccharide consisting of d-glucose linked by β-glycosidic bonds using heterogeneous catalysts under mild reaction conditions. The use of alkaline earth metal oxide solid base catalysts like CaO and MgO in the presence of hydrogen peroxide could afford formic acid from cellobiose at 343 K. While CaO gave 14 % yield of formic acid, the oxide itself was converted to a harmful metal peroxide, CaO<inf>2</inf> after the reaction. In contrast, MgO could produce formic acid without the formation of the metal peroxide. The difficulty in selectively synthesizing formic acid from cellobiose using these solid base catalysts was due to the poor conversion of cellobiose to glucose. Using a combination of solid acid and base catalysts, a high formic acid yield of 33 % was obtained under mild reaction conditions due to the quantitative hydrolysis of cellobiose to glucose by a solid acid followed by the selective decomposition of glucose to formic acid by a solid base.

DOI： 10.1002/open.202400079

Web of Science

Scopus

PubMed

researchmap

記述言語：英語   出版者・発行元：Wiley-VCH GmbH  

Formic acid is considered a promising hydrogen carrier. Biomass-derived formic acid can be obtained by oxidative decomposition of sugars. This study explored the production of formic acid from cellobiose, a disaccharide consisting of d-glucose linked by β-glycosidic bonds using heterogeneous catalysts under mild reaction conditions. The use of alkaline earth metal oxide solid base catalysts like CaO and MgO in the presence of hydrogen peroxide could afford formic acid from cellobiose at 343 K. While CaO gave 14 % yield of formic acid, the oxide itself was converted to a harmful metal peroxide, CaO2 after the reaction. In contrast, MgO could produce formic acid without the formation of the metal peroxide. The difficulty in selectively synthesizing formic acid from cellobiose using these solid base catalysts was due to the poor conversion of cellobiose to glucose. Using a combination of solid acid and base catalysts, a high formic acid yield of 33 % was obtained under mild reaction conditions due to the quantitative hydrolysis of cellobiose to glucose by a solid acid followed by the selective decomposition of glucose to formic acid by a solid base.

CiNii Research

掲載種別：研究論文（学術雑誌）   出版者・発行元：ACS Applied Energy Materials  

Metal-supported protonic ceramic fuel cells were prepared, and the effects of a double columnar layer at the cathode side of BaZr0.44Ce0.36Y0.2O3 (BZCY) on power density and open-circuit voltage (OCV) were studied. The double columnar structure of Pr0.2Ce0.8O2 (PrDC) and BZCY was prepared with pulsed laser deposition. It was found that the insertion of the double columnar layer was highly effective for increasing the power density and OCV. The optimum composition of the double columnar was BZCY:PrDC = 7:3, with a thickness of 200 nm. The power density of PCFCs with the BZCY-PrDC double columnar reached 413 mW/cm2, and the OCV was approximately 1.05 V at 873 K, which is six times higher than that of a cell without a functional layer. The high power density of the cell was attributed to the decreased overpotential of the cathode. Therefore, the BZCY-PrDC double columnar layer is effective in expanding the reaction site by increasing the proton concentration at the cathodic interface.

DOI： 10.1021/acsaem.4c01529

Web of Science

Scopus

researchmap

掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Materials Chemistry A  

Aqueous dual-ion batteries have good safety, environmental compatibility, and low cost due to the use of an aqueous electrolyte. However, water electrolysis occurs during charging at high potential, resulting in a poor cyclic stability of aqueous dual-ion batteries. Hence, novel anode materials are urgently needed to be developed for aqueous dual-ion batteries with low water electrolysis. A niobium-based binary-phase composite material is reported with a capacity of 135 mA h g−1 at a current density of 0.2 mA cm−2 and with excellent reversibility in the potential range of −1.3-0 V vs. Ag/AgCl. The activation energy of Li+ intercalation was obviously decreased because of the formation of an interface, which enhanced the Li+ intercalation reaction between FeNbO4 and MoNb12O33. In addition, the lower amount of Fe2+ in the lattice of MoNb12O33 caused localized compressive strain, which promoted fast Li+ diffusion in MoNb12O33. A full dual-ion battery of 3.0 V was constructed using the binary-phase niobium-based composite for the anode, and demonstrated a high cycle stability and an average coulombic efficiency of 91% over 300 cycles. Furthermore, considering both the electrolyte and electrode materials, the theoretical energy density of this dual-ion battery was estimated to be 250 W h kg−1, which is close to that of the current Li-ion rechargeable battery.

DOI： 10.1039/d4ta01293c

Web of Science

Scopus

researchmap

掲載種別：研究論文（学術雑誌）   出版者・発行元：ACS Sustainable Chemistry and Engineering  

[FeFe]-hydrogenase (HydA) is an active biocatalytic enzyme for solar-to-hydrogen (H2) conversion. However, stability is a main challenge that limits practical applications. This work aims to encourage the efficiency of HydA by encapsulating it in the zeolitic imidazolate framework-8 (ZIF-8) as a synthetic protective shield. The construction of HydA@ZIF-8 nanoparticles, with an average diameter of 700-1000 nm, at ambient conditions can preserve HydA activity within a spatially confined microenvironment, as characterized by scanning electron microscopy and X-ray diffraction analysis. Based on MV•+-dependent H2 production activity and kinetic analysis, both the stability and efficiency of HydA@ZIF-8 surpass those of free HydA and whole-cell biocatalysts over a wider range of pH and temperature. The achievement of robust HydA@ZIF-8 construction represents a significant step forward in the development of biocatalysts for various future applications.

DOI： 10.1021/acssuschemeng.3c08560

Web of Science

Scopus

researchmap

出版者・発行元：Solar RRL  

Perovskite solar cells (PSCs) have undergone an unprecedentedly rapid development in both power conversion efficiency (PCE) and operational durability. However, a number of unknown challenges remain before PSC products are ready to launch. Herein, it is demonstrated that the vacuum deposition of gold (Au) onto the organic hole-transport layer (HTL) results in Au penetration into the perovskite layer. This Au penetration proves to be a limiting factor in PCE due to detrimental carrier recombination caused by the penetrated Au component inside the perovskite light absorber. To mitigate this issue, a thin molybdenum oxide (MoOx) interlayer between the organic HTL and the Au electrode is introduced, effectively reducing the Au penetration and suppressing the carrier recombination. Consequently, this MoOx introduction increases PCEs from ≈16.9% to ≈19.6% by ≈2.7%. Furthermore, using the MoOx interlayer improves the long-term durability of PSCs. These findings are crucial in elucidating a basic mechanism that limits PCE and in advancing the fabrication of PSC products with even higher performance.

DOI： 10.1002/solr.202400029

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人　電気化学会  

A dense NiO-Fe2O3 (NiFe) pellet has been developed as a potential anode-support for thin-film solid oxide fuel cells (SOFCs). However, preparation of dense NiFe is very challenging. Hole-formed NiFe pellets or porous NiFe pellets are frequently formed, which cannot be used as a support (substrate) for thin-film SOFCs. Therefore, this hole-formed NiFe support is simply wasted. In this report, we attempt to re-qualify this NiFe support to be a valuable substrate, which can be used for fabricating thin-film SOFCs. By deposition of smaller NiFe particles to cover the hole-formed NiFe support, the surface of this NiFe pellet is modified. Large holes on the surface disappear. The newly formed NiFe support can be used for fabricating a single cell with La0.9Sr0.1Ga0.8Mg0.2O3−δ as thin-film electrolyte operated at intermediate temperature. Maximum power density generated from this cell is 0.45, 0.86 and 1.28 W cm−2 at 873, 923 and 973 K, respectively. (Figure Presented).

DOI： 10.5796/electrochemistry.23-00164

Web of Science

Scopus

CiNii Research

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

出版者・発行元：Solar RRL  

All-inorganic CsPbI2Br mixed halide perovskites show promise as wide-bandgap photoabsorbers in photovoltaics. However, the rapid crystal growth observed in solution-processed CsPbI2Br often leads to morphologies plagued by pinholes and defects, which limit device performance. This study introduces 2-Amino-5-nitrothiazole (ANT), an innovative precursor additive, to enhance film quality. ANT's selective interactions with the perovskite precursor moderate the crystal growth, resulting in a dense, flawless CsPbI2Br film characterized by superior crystallinity and coverage. Furthermore, the -NH2 group in ANT coordinates with Pb octahedra, effectively mitigating charge defects through NH=I/Br bonds. Simultaneously, S=C-N sites interact with uncoordinated Pb2+ ions, reducing defect states and nonradiative recombination. This innovation achieves an impressive device efficiency of 17.13% with a fill factor (FF) of 83.41%, surpassing the control's efficiency of 15.21% (FF of 80.45%). Notably, the champion device maintains an efficiency of 29.47% under indoor light-emitting diode lighting at 1000 lux. Additionally, the optimized perovskite solar cell demonstrates remarkable stability, retaining ≈90% of its efficiency for over 720 h at 85 °C in air, even without encapsulation.

DOI： 10.1002/solr.202300912

Web of Science

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Catalysis B: Environmental  

NH3 is an important chemical fertilizer and expecting as H2 carrier. Several methods have been investigated for eco-friendly NH3 production under mild conditions instead of Haber-Bosch process using 400 °C, 20 MPa. Here, cyanobacterial Anabaena variabilis was utilized as a nitrogenase-producing biocatalyst that converts N2/H2O to NH3 under ambient conditions. Biocatalytic reactions revealed that MV•+ can penetrate cell membrane and transfer electrons generated in inorganic photocatalyst. We first reported photobiocatalytic NH3 production of cyanobacteria and TiO2. Comparing with natural system, NH3 formation rate of the hybrid system increased 81.3 times with an initial rate of 2031.7 nmol·h−1 and turnover number of 216.8.

DOI： 10.1016/j.apcatb.2023.123431

Web of Science

Scopus

researchmap

出版者・発行元：International Journal of Energy Research  

The processing of halide perovskites in the air significantly influences their morphology and surface coverage, often leading to the presence of numerous trap densities that adversely affect device performance. In this study, we explored the development of perovskite films using a solvent extraction method, where the temperature of the anisole antisolvent was varied. Our findings demonstrate that the hot-antisolvent strategy effectively controls nucleation, resulting in the formation of highly dense, pinhole-free, and crack-free perovskite films with reduced surface roughness. Films fabricated using this hot-antisolvent approach exhibited enhanced photoluminescence, indicating lower trap density and increased recombination resistance. They also showed slower charge carrier recombination rates and efficient charge extraction, suggesting the suppression of nonradiative recombination. Furthermore, the superior quality of perovskite films obtained through the hot-antisolvent strategy significantly enhanced the power conversion efficiency (PCE) of hot-pressed semitransparent perovskite solar cells. The PCE remarkably increased from 0.13% to an impressive 12.65% while maintaining an average visible transmittance of 26.55% and exceptional air stability for 2000 hours with no significant degradation in initial PCE. This study achieves a record-breaking light utilization efficiency of 3.36% in the realm of research on hot-press processes.

DOI： 10.1155/2024/9417829

Web of Science

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Electrochemical Society  

Effects of channel size in NiO-YSZ porous substrate were studied on power density in solid oxide fuel cell mode and electrolysis current in steam electrolysis mode. It was found that the cell deposited on anode substrate with larger pore diameter shows a superior performance. The LSGM cell prepared on Ni-YSZ tube with average channel diameter of ca. 2.5 μm shows the maximum power density of 0.36 W cm−2 in SOFC mode and 0.42 A cm−2 at 1.6 V in SOEC mode at 873 K. Spike potential noise which may be caused by insufficient gas diffusion in NiO-YSZ porous substrate was observed under constant current electrolysis condition in case of NiO-YSZ tube with narrow channel and the spike noise is suppressed by increasing channel size. NiO-YSZ tube with large channel size is also effective for increasing long term stability in electrolysis mode.

DOI： 10.1149/1945-7111/ad2815

Web of Science

Scopus

researchmap

その他リンク： https://iopscience.iop.org/article/10.1149/1945-7111/ad2815/pdf

掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Materials Chemistry C  

In this study, a hybrid photocatalyst with titanium oxide using reduced graphene nanoribbons (rGNR) was fabricated. The resulting 0.5 wt% platinum-loaded titanium oxide-supported reduced GNRs (Pt/TiO2/rGNR) exhibited an activity of 2.54 mmol h−1 g−1 which is 6.35 times higher than the 0.40 mmol h−1 g−1 of the titanium oxide photocatalyst. This activity was also higher than that of the starting material, multi-walled carbon nanotube (MWCNT)-supported titanium oxide (Pt/TiO2/MWCNT) as 0.80 mmol h−1 g−1. The resulting catalysts were characterized by X-ray photoelectron spectroscopy (XPS) and fluorescence lifetime spectroscopy, and the GNRs chemically reduced by NaBH4 (rGNR) had higher conductivity than the GNRs reduced by photogenerated electrons (pGNR) from titanium oxide. It was found using the photocatalytic reaction and photocurrent test that almost no photoresponsivity of reduced GNR character was exhibited. This result clarified that the reduced GNRs played the role of a mediator that promotes charge separation between photocatalysts and that effective hydrogen production in water was achieved.

DOI： 10.1039/d3tc03622g

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）   出版者・発行元：Catalysis Today  

Photocatalytic hydrogen peroxide (H2O2) by oxygen and phosphorus co-doped graphitic carbon nitride (C3N4) with cobalt phosphate (CoP) cocatalyst is investigated. The photocatalyst powder of CoP-C3N4 1:n, n = 0–4, n is the weight ratio of cyanuric acid added) was synthesized by melamine cyanurate template method. Characterization of the catalyst was performed by X-ray diffraction analysis, and scanning electron microscopy, X-ray photoemission spectra, and fluorescence decay spectra. Oxygen doping was performed by the melamine and cyanuric acid template method, followed by phosphorus doping of the C3N4 backbone by the introduction of CoP. Co-doping of O and P atom facilitated charge transfer on the C3N4 backbone, while CoP facilitated charge separation at the C3N4 interface. The CoP-C3N4 (1:4) photocatalyst increased H2O2 production rate by 293 % compared to that of the cyanuric acid-free photocatalyst and also achieved the photocatalytic oxygen evolution from water. These results indicate that O,P co-doped CoP-C3N4 can perform sacrificial agent-free hydrogen peroxide under visible light irradiation.

DOI： 10.1016/j.cattod.2023.114400

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）   出版者・発行元：Solid State Ionics  

Mullite-phase bismuth gallate (Bi2Ga4O9) was successfully synthesized with partial substitution of bismuth with alkaline-earth cation, Mg2+, Ca2+, Sr2+, and Ba2+. The effect of this substitution on the electrical conductivity was investigated. In this study, substitution with Ca2+ of Bi site was further studied for increasing the ionic conductivity as well as the phase stability in reducing atmospheres. Substitution with Ca2+ was found to be the most effective and with 12.5 mol% of Ca2+ as the optimized doping amount. Conductivity and stability in reducing atmospheres was increased down to pO2 ≤ 10−19 atm while keeping the conductivity of σ = 2.6 × 10−2 S·cm−1 at 973 K largely independent of oxygen partial pressure. Oxygen permeation analysis estimates 76% of theoretical oxygen permeation rate at 973 K suggesting main charge carrier is oxide ion. Partial electronic conductivity was measured with the ion blocking method. Oxide ion conductivity is dominated over wide pO2 range excepting for hole conduction at high pO2. Density functional theory (DFT) analysis on oxide ion diffusion route suggests oxygen hoping through lattice vacancy is main pathway for oxide ion conductivity in this doped Bi2Ga4O9. Despite the low oxide ion conductivity in Mullite-phase oxide, it was found that Ca doped Bi2Ga4O9 shows good oxide ion conductivity over wide pO2 range.

DOI： 10.1016/j.ssi.2023.116343

Web of Science

Scopus

researchmap

出版者・発行元：Applied Surface Science  

All-inorganic α-CsPbI2Br perovskite has garnered considerable interest due to its optical bandgap (∼1.92 eV) suitable for tandem architectures and superior thermal stability. However, CsPbI2Br based perovskite solar cells (PSCs) exhibit severe energy loss due to presence of various surface defects like uncoordinated Pb2+ ions, halide ion vacancies and pinholes, which causes serious non-radiative recombination and limit the further improvement in power conversion efficiency (PCE). Surface passivation strategy is an effective approach to produce high quality α-CsPbI2Br film. Herein, we introduce fluorinated ionic liquid, 3-(Trifluoromethyl) benzylamine (CFBA), as surface passivating agent. The chemical analysis shows that the trifluoro (-CF3) and amine groups of CFBA strongly interacted with perovskite surface via forming Pb-F and H-I bonding, respectively. The high electronegative fluoride atoms of -CF3 group allow for electrostatic interaction with uncoordinated Pb2+ ions, which built a robust shield that protected against surrounding moisture as well. In addition, CFBA modification passivates the dangling bonds, enhanced crystallinity, reduced pinholes, improved the surface coverage and compactness, increased hydrophobicity, and decreased non-radiative recombination, leading to high PCE. With optimum concentration of 3 μL-CFBA, CsPbI2Br PSC revealed an impressive PCE of 17.07% with FF of 83.21% as compared to pristine device (PCE of 15.24% with FF of 79.81%). Moreover, champion device showed an excellent thermal stability by retaining ∼ 86.23% of its initial PCE, whereas pristine device maintained ∼ 48.26% of its original PCE after 1440 h aging at 85 ℃ in a dry box without any encapsulation. In addition, optimized PSC showed a decent indoor PCE of 23.24% as compared to pristine device (18.35%) under dim lighting conditions (LED, 3200 K) at 1000 lx. These results suggested that surface passivation strategy with CFBA is a promising approach for developing efficient all-inorganic CsPbI2Br outdoor/indoor PSCs with better thermal stability.

DOI： 10.1016/j.apsusc.2023.157901

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Materials Chemistry A  

BODIPY (boron-dipyrromethene) compounds are extensively utilized in various applications. Typically, their activity is modified by altering the functional groups at the α-, β-, and meso-positions of the substituents. However, no systematic information has been provided regarding the effects of substituted F- positions and hydrophobicity on the activity of BODIPY sensitizers in photosensitizing chemistry. Dyes (7a-7c) with different alkyl chain lengths were synthesized and compared with the unsubstituted compound 3 to discuss the effects of -F position substituents and the hydrophobicity of BODIPY dyes on photocatalytic activity. Density functional theory (DFT) calculations showed that -F-substitution induced an intramolecular charge transfer (ICT) effect, enhancing visible-light absorption. Longer alkyl chains provided a favourable second coordination sphere reaction environment for hydrogen production. Experimentally, dye 7c demonstrated the highest activity, with a hydrogen production rate of 496.5 μmol gcat−1 h−1, which is 3 times higher than that of 3, and a 9.6 times higher turnover frequency (TOF) than that of 3. The apparent quantum yield (AQY) at 650 nm was 1.4%. This study highlights the importance of -F position substitution and optimizing hydrophobicity to enhance the photocatalytic activity of metal-free organic dyes through the creation of a new second coordination sphere.

DOI： 10.1039/d3ta03682k

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Solid State Ionics  

For increasing the performance of PCFC (Protonic Ceramic Fuel Cells), it is important to prepare high-quality thin films of electrolyte materials. In this study, the preparation condition of the thin film of BaZr0.8Yb0.2O2.9 (BZYb) by pulsed laser deposition (PLD) method was optimized and the electrical conductivities of the obtained films were measured. The thin film was prepared by PLD using two kinds of BZYb targets, which were prepared by solids state reaction and Pechini method. Both thin-film samples have the single phase of the cubic perovskite-type structure, however, morphology as well as the orientation of the BZYb film was significantly different. The thin film using the target material by Pechini method is a high crystalline orientation and partially oriented [211] direction. The electrical conductivities of the obtained thin films at reduction atmosphere are dominated by proton conductivity, which is almost the same as that of the bulk sample despite [211] orientation.

DOI： 10.1016/j.ssi.2023.116240

Web of Science

Scopus

researchmap

リポジトリ公開URL： https://hdl.handle.net/2324/7172331

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Catalysis A: General  

Photobiocatalytic system has been developing as a promising approach for H2 production. Herein, the rational characteristics of biocatalysts and the role of individual components affecting the efficiency of the system were investigated. Photocatalytic studies showed that tris (2-amino-2-hydroxymethyl-1,3-propanediol) was an ideal electron donor for viologen reduction by TiO2. Biocatalytic reaction revealed that cell permeability, the redox potential of electron mediators and the cell envelope were crucial to the activity of whole-cell biocatalysts. In photobiocatalytic system, recombinant Escherichia coli with a turnover frequency of 39.43 ± 3.77 s−1 based on [FeFe]-hydrogenase activity was a more rational biocatalyst than Anabaena variabilis. A comprehensive study found that the presence of TiO2, light and biocatalysts strongly enhanced H2 production, whereas Tris and MV2+ had less influence. A maximum rate was found at 16.73 ± 1.03 μmol/min with a solar-to-H2 conversion of 1.58 ± 0.10 %. Understanding the role of each component will guide the development of high-efficient photobiocatalysis.

DOI： 10.1016/j.apcata.2022.119019

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Physics A: Materials Science and Processing  

Squaraine dyes are organic dyes having strong and narrow absorption properties in the near-infrared region that are widely used in photovoltaic and biomedical applications. In this work, squaraine dye (SA1) was synthesized as a dye sensitizer for a dye-sensitized photocatalytic system, which was composed of SA1 and Pt-loaded TiO2 powder photocatalyst (SA1/Pt-TiO2). The SA1/Pt-TiO2 system exhibited a good hydrogen production performance within 150 h and an apparent quantum yield of 1.4% under 800 nm monochromatic light irradiation. However, during the photocatalytic reaction, the photocatalytic activity of SA1/Pt-TiO2 decreased due to photodecomposition. Ultraviolet–visible absorption spectroscopy, 1H nuclear magnetic resonance spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry measurements were performed to investigate the mechanism of the decomposition of the squaraine moiety of SA1, the decomposition process, and the structure of the decomposed material. The results show that even without the Pt-loaded TiO2 powder photocatalyst, SA1 undergoes photodissociation, which cleaves the bond between the indoline moiety and the square acid. Graphical abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s00339-022-06281-7

Web of Science

Scopus

researchmap

その他リンク： https://link.springer.com/article/10.1007/s00339-022-06281-7/fulltext.html

掲載種別：研究論文（学術雑誌）   出版者・発行元：Catalysis Science and Technology  

Strained metal oxides are known to exhibit improved activity for redox and photocatalytic reactions. Here, we intentionally introduced tensile strain into rutile-type TiO2 by utilizing the difference in thermal expansion coefficients between TiO2 and Au and applied it as a solid acid catalyst. It was demonstrated that its acid catalytic activity in the acetalization of furfural was enhanced by increasing the degree of the strain introduced.

DOI： 10.1039/d2cy00736c

Web of Science

Scopus

researchmap

記述言語：日本語   出版者・発行元：公益社団法人 石油学会  

<p>白金担持アルミナ上で，一酸化窒素（NO）を酸化剤としてメタンをシアン化水素（HCN）に変換する際の白金ナノ粒子の粒径効果について検討した。担持量と焼成温度を制御することにより，1.6〜4.1 nmの範囲で様々な平均粒子径のPt触媒を得ることができた。Pt表面サイト量はパルス法によるCO滴定で決定し，触媒活性は同一接触時間下で評価した。Pt の粒子が小さい触媒（1.6〜3.2 nm）では，NO 転化率が粒子径の大きい触媒よりも低いことが分かった。粒子径の大きな触媒（4.1〜4.2 nm）は，10 wt% Pt/Al₂O₃ において 400 ℃で 収率1.3 %（炭素ベース）で高い HCN 選択率（53.5 %）を示した。大きなPt粒子が高い活性を示す理由の一つは，金属と担体の界面で進行するHCNから二酸化炭素とアンモニアへの逐次反応を抑制したためと思われる。Pt L₃端X線吸収微細構造（XAFS）スペクトルから，反応試験後の小粒子触媒はPt–CN種で覆われていることが分かった。一方，大粒子触媒ではPt–COが主な吸着種として観測され，大粒子触媒の方がHCN脱離が容易であることが示唆された。</p>

DOI： 10.1627/jpi.65.184

Web of Science

Scopus

CiNii Research

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Solid State Ionics  

NiO-Y2O3 stabilized ZrO2 (YSZ) tubular type cell using La0.9Sr0.1Ga0.8Mg0.2O3−δ electrolyte film was prepared by dip-coating method. Effects of Ce infiltration or Ce, Ni sequential-infiltration into NiO-YSZ substrate were studied and it was found that Ce infiltration after Ni is highly effective for increasing the cell performance and the stability in fuel cell and electrolysis mode at 873 K in spite of decrease in performance by simple Ni infiltration. Cyclic operation of the fuel cell and electrolysis of LSGM tubular cell using Ce or Ce[sbnd]Ni sequential-infiltrated NiO-YSZ substrate was measured at 873 K using 17% steam-25%H2 in Ar as fuel. After 100 cycles at ±0.1 A cm−2, OCV was almost the same with the initial value. The terminal potential in SOFC operation became slightly lower with increasing cycle number in case of simple Ce infiltration. The main reason for degradation during cyclic performance seems to be assigned to the increased fuel electrode overpotential. However, degradation rate is much decreased by Ce[sbnd]Ni sequential-infiltration.

DOI： 10.1016/j.ssi.2022.115914

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Catalysis A: General  

Porous boron nitride was synthesized using boric acid with urea and/or hexamethylenetetramine (HMTA) via pyrolysis method. X-ray diffraction and Fourier transform infrared measurements indicated that the synthesized boron nitride has a turbostratic structure with both amino and hydroxyl group on the surface. The synthesis using a mixture of two nitrogen-containing precursors was found to not only significantly increase the porosity, but also improve the surface functionality. X-ray photoelectron spectroscopy and B K-edge and O K-edge X-ray absorption fine structure measurements revealed that the proportion of amino and hydroxyl groups on the surface increased with increasing concentration of HMTA during synthesis. Solid-state 11B nuclear magnetic resonance spectroscopy indicated that all samples contained trigonal B-N, trigonal B-O and tetrahedral B-O sites, and that samples prepared with high concentrations of HMTA had less tetrahedral B-O sites, suppressing the formation of BOx species as byproducts. Solid base catalytic activity was evaluated through Knoevenagel condensation, and the catalytic performance was significantly improved by synthesizing boron nitride catalyst using a mixture of the two nitrogen-containing precursors. The enhancement of the activity was influenced by the development of the pore structure as well as the emergence of functional groups on the surface.

DOI： 10.1016/j.apcata.2022.118635

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Materials Chemistry A  

Sillén-Aurivillius phase Bi4NbO8Cl consists of Bi2O2+/NbO3-/Bi2O2+/Cl- layers and oxide-ion conduction is expected to occur in its Bi2O2+ layer. Here, we report the influence of partial substitutions of Bi with Ca2+, Sr2+, Ba2+, La3+, Ga3+ and Sn4+ on the electrical properties. It was found that substitution with low valence cations is effective for increasing electrical conductivity, and in particular, Sr2+ substitution is the most effective for this purpose. The dependence of electrical conductivity on the oxygen partial pressure of a Sr-doped sample is quite low (PO2-0.015) and the optimized amount of Sr doping is x = 0.1 in Bi4-xSrxNbO8-δCl. The electromotive force of N2/O2 gas concentration cell is 90% of the theoretical value and the tracer diffusion constant (D) estimated by 18O2 diffusion almost corresponds with that estimated from conductivity. Considering the activation energy of the D value, oxide-ion conductivity in Sillén-Aurivillius phase Bi4NbO8Cl mainly occurs along the Bi2O22+ layer, which indicates that Bi4NbO8Cl is a new family of fast oxide-ion conductors. This journal is

DOI： 10.1039/d1ta07335d

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.cej.2021.131063

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

SrTiO3 is a well-known highly active photocatalyst with high energy conversion efficiency. In this study, we investigated the formation of oxygen vacancy by using the chemo-mechanical effect that was introduced by the dispersion of metal particles into grain and photocatalytic activity to water splitting. Au dispersion on SrTiO3 followed by sintering treatment was studied for introduction of chemo-mechanical strain because of a different thermal expansion coefficient; the introduced chemo-mechanical strain generated oxygen vacancy in SrTiO3. Thus, induced chemo-mechanical strain shows change in electronic band structure resulting in increasing lowest unoccupied molecular orbital (LUMO) level with increasing Au content. Since photoluminescence was significantly decreased by sintering after Au dispersion, the introduced strain effects may work for increasing a charge separation efficiency and adsorption site in water splitting. Therefore, the photocatalytic activity was much increased by sintering treatment after Au dispersion on SrTiO3.

DOI： 10.1016/j.apcatb.2020.119292

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.apcata.2020.117843

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Selective conversion of CO2 to fuels and chemicals has been considered one of the key challenges in the electrochemical CO2 reduction reaction (CO2RR). Here, we demonstrate the reaction pathways for CO and C2H4 formation on Cu can be regulated by supplying different CO2 partial pressures. Although it is believed high concentration of surface bound CO is required for C2H4 formation, we show excessive supply of CO2 interferes with C-C coupling and suppress C2H4 reaction pathways. This indicates C2H4 reaction pathways are limited by the surface recombination of surface bound CO and hydrogen, and the kinetics is affected by adsorbate-adsorbate interactions and/or by physical blocking of active sites on Cu with excess CO2. Through systematic study, we demonstrate a dilute CO2 stream selectively activates C2H4 formation with significant reduction of the overpotentials (similar to 400 mV) to achieve similar to 50% C2H4 Faradaic efficiency and enhancement in the C2H4 current density (similar to 50 mA cm(-2)).

DOI： 10.1016/j.apcatb.2020.119049

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Electrochemical CO production from CO2 electrolysis has been considered the most economically viable approach among various candidate products. AuCu bimetallic alloys are currently receiving attention for their potential to tailor catalytic activity. Here, we synthesized a dilute AuCu alloy nanostructure with an AuCu atomic composition ratio of 3% by using a simple electrochemical treatment method on a 200 nm-thick Au thin film. The dilute AuCu alloy catalyst shows an exceptional CO2 reduction activity in terms of selectivity and overpotential for CO production. In addition, the stability property is more significantly enhanced as compared to pure Au nanostructures. In addition, we describe an in situ tailoring method of catalytic activity for Au nanostructures by repeating an electrochemical treatment process that is performed for forming the Au nanostructure. This approach will be a promising and facile strategy not only for reactive Au catalysts but also to increase the stability activity simultaneously by utilizing Cu impurities existing in an aqueous electrolyte for CO2 reduction.

DOI： 10.1063/5.0009340

記述言語：その他  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Direct decomposition of NO on Ba3Y4O9 doped with Cu and Sc was studied and it was found that co-doping of Sc and Cu into Ba3Y4O9 was effective for increasing both lattice stability and NO decomposition activity. In particular, Ba3Y3Sc0.6Cu0.4O9 (10 % Cu and 15 % Sc doping) catalyst showed N-2 and O-2 yield of 90 % and 99 %, respectively, in NO decomposition reaction at 700 degrees C. Comparing with the pristine and single-metal doped system, the optimized catalyst showed superior long-term stability and increased activity under O-2, and water vapor co-existence conditions because of the increased stability of crystal structure, improved lattice oxygen mobility and weakened oxygen adsorption on the surface. TPD and in-situ FT-IR results suggested that the co-doping effect was assigned to the easier removal of surface NO2- or NO3- species which blocks the active site to NO decomposition.

DOI： 10.1016/j.apcata.2020.117743

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Dye-sensitized photocatalytic hydrogen production using a boron-dipyrromethene (BODIPY) organic material having a pyridyl group at the anchor site was investigated. Phenyl, carbazole, and phenothiazine derivatives were introduced into BODIPY dyes, and their photocatalytic activities were examined. Identification was performed by nuclear magnetic resonance (NMR), infrared (IR), mass (MS) spectra, and absorption spectra, and catalyst evaluation was performed by using visible-light irradiation and photocatalytic hydrogen production and photocurrent. These dyes have strong absorption at 600-700 nm, suggesting that they are promising as photosensitizers. When the photocatalytic activity was examined, stable catalytic performance was demonstrated, and the activity of the Pt-TiO(2)photocatalyst carrying a dye having a carbazole group was 249 mu mol/g(cat)center dot h. Photocurrent measurements suggest that dye-sensitized photocatalytic activity is occurring. This result suggests that BODIPY organic materials with pyridyl groups as anchor sites are useful as novel dye-sensitized photocatalysts.

DOI： 10.3390/catal10050535

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We report for the first time to our knowledge the identification of heteroatom-doped and undoped C3N4 with the energy-resolved distribution of electron traps (ERDT) near the conduction band bottom position (CBB) using reversed double-beam photoacoustic spectroscopy. The ERDT/CBB pattern is used to classify the type of elemental doping in C3N4, related to photocatalytic efficiency.

DOI： 10.1039/c9cc09988c

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Electrocatalytic CO2 reduction is a promising way to provide renewable energy from gaseous CO2. The development of nanostructures improves energy efficiency and selectivity for value-added chemicals, but complex nanostructures limit the CO2 conversion rates due to poor mass transport during vigorous electrolysis. Herein, we propose a three-dimensional (3D) hierarchically porous Au comprising interconnected macroporous channels (200-300 nm) and nanopores (similar to 10 nm) fabricated via proximity-field nanopatterning. The interconnected macropores and nanopores enable efficient mass transport and large active areas, respectively. The roles of each pore network are investigated using reliable 3D nanostructures possessing controlled pore distribution and size. The hierarchical nanostructured electrodes show a high CO selectivity of 85.8% at a low overpotential of 0.264 V and efficient mass activity that is maximum 3.96 times higher than that of dealloyed nanoporous Au. Hence, the systematic model study shows the proposed hierarchical nanostructures have important value in increasing the efficiency of expensive Au.

DOI： 10.1073/pnas.1918837117

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Development of efficient and selective electro-catalysts is a key challenge to achieve an industry-relevant electrochemical CO2 reduction reaction (CO2RR) to produce commodity chemicals. Here, we report that Au-25 clusters with Authiolate staple motifs can initiate electrocatalytic reduction of CO2 to CO with nearly zero energy loss and achieve a high CO2RR current density of 540 mA cm(-2) in a gas-phase reactor. Electrochemical kinetic investigations revealed that the high CO2RR activity of the Au-25 originates from the strong CO2 binding affinity, leading to high CO2 electrolysis performance in both concentrated and dilute CO2 streams. Finally, we demonstrated an 18.0% solar-to-CO conversion efficiency using a Au-25 electrolyzer powered by a Ga0.5In0.5P/GaAs photovoltaic cell. The electrolyzer also showed 15.9% efficiency and a 5.2% solar-driven single-path CO2 conversion rate in a 10% CO2 gas stream, the CO2 concentration in a typical flue gas.

DOI： 10.1021/acsenergylett.9b02511

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, ZnTi-mixed metal oxides (ZTM), such as ZnTiO3, were synthesized from ZnTi layered double hydroxides by varying the molar ratio of Zn/Ti, calcination temperatures, and synthesis methods (hydrothermal or reflux). The surface electronic characteristics of ZTM were investigated by the energy-resolved distribution of electron traps (ERDTs) using reversed double-beam photoacoustic spectroscopy. The ZTM samples obtained by conducting hydrothermal synthesis at 500 degrees C showed similar ERDT patterns independent of the molar ratio of Zn/Ti, although ZnTiO3 phase was not observed in the X-ray diffraction pattern, when the Zn/Ti ratio was high. When the ERDT patterns demonstrated a high electron accumulation level near the conduction band bottom in hydrothermal products at 500 degrees C, a higher photocatalytic phenol degradation efficiency was observed due to the formation of ZnTiO3 phase. This suggested that the product with the high Zn/Ti molar ratio (Zn/Ti = 6) constituted amorphous ZnTiO3.The enhanced photocatalytic performance of ZTM could be attributed to the heterojunction of electrons among ZnO, TiO2, and ZnTiO3, which enabled electron transfer in the composites, prevented charge recombination, and promoted a wider visible light adsorption by ZnTiO3 phase irrespective of its crystallinity.

DOI： 10.1021/acsami.9b18785

記述言語：英語  

Electrochemical CO2 conversion offers a promising route for value-added products such as formate, carbon monoxide, and hydrocarbons. As a result of the highly required overpotential for CO2 reduction, researchers have extensively studied the development of catalyst materials in a typical H-type cell, utilizing a dissolved CO2 reactant in the liquid phase. However, the low CO2 solubility in an aqueous solution has critically limited productivity, thereby hindering its practical application. In efforts to realize commercially available CO2 conversion, gas-phase reactor systems have recently attracted considerable attention. Although the achieved performance to date reflects a high feasibility, further development is still required in order for a well-established technology. Accordingly, this review aims to promote the further study of gas-phase systems for CO2 reduction, by generally examining some previous approaches from liquid-phase to gas-phase systems. Finally, we outline major challenges, with significant lessons for practical CO2 conversion systems.

DOI： 10.3390/catal9030224

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Increasing the surface area to improve chemical activity is an unending task from conventional catalysis to recently emerging electrochemical energy conversion and storage. Here, a simple, vacuum-deposition-based method to form nanoporous structures of metals is reported. By utilizing thermal evaporation at a high pressure, fractal-like nanoporous structures of Sn with porosity exceeding 98% are synthesized. The obtained nanostructure consists of nanoparticle aggregates, and the morphology can be controlled by adjusting the working pressure. The formation of the nanoporous structure is explained by homogeneous nucleation and diffusion-limited aggregation, where nanoparticles produced by the repeated collisions of evaporated atoms adhere to the substrate without diffusion, forming porous aggregates. Due to the easy oxidation of Sn, the constituent nanoparticles are covered with amorphous SnOx and crystalline SnO phases. When the nanoporous Sn/SnOx aggregates are applied to a lithium-ion battery anode through direct deposition on a Cu foil current collector without binders or conducting additives, the nanoporous Sn/SnOx anode shows greatly enhanced cyclability and exceptional rate performance compared to those of a dense Sn thin film anode. The approach investigated in this work is expected to provide a new platform to other fields that require highly porous structures.

DOI： 10.1002/ppsc.201800331

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Cobalt oxide (CoOx), an earth-abundant and low-cost oxygen evolving catalyst (OEC), has notable advantages as a top protection layer of photoanodes for solar-driven water oxidation because of its desirable durability. However, cobalt oxides exist as various phases, such as Co(II)O, Co2(III)O3, Co3(II,III)O4, and the (photo)electrochemical properties of CoOx are significantly governed by its phase. Atomic layer deposition (ALD) is a suitable method to form a multifunctional layer for photoelectrochemical (PEC) water splitting because it allows direct growth of a conformal high-quality film on various substrates as well as facile control over its chemical phases by adjusting the deposition conditions. Here, a well-controlled CoOx/SiOx/n-Si heterojunction prepared by ALD is demonstrated for solar-driven water splitting. The phase of the ALD CoOx films can be easily controlled from CoO to Co3O4 by varying the deposition temperature. In addition, this systematic study reveals that its energetic as well as electrochemical properties are changed significantly with the phase. Whereas CoO grown at 150 degrees C produces high photovoltage by building desirable hole-selective heterojunctions with n-Si, Co3O4 formed at 300 degrees C has a better catalytic property for water oxidation. To address this competitive correlation, we developed a double-layered (DL) ALD CoO, film that has advantages of both CoO and Co3O4. The DL ALD CoOx/SiOx/Si heterojunction photoanode produces a photocurrent density of 3.5 mA/cm(2) without a buried junction and maintains a saturating current density of 32.5 mA/cm(2) without noticeable degradation during 12 h in 1 M KOH under a simulated 1 sun illumination.

DOI： 10.1021/acscatal.8b03520

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Mass transfer, kinetics, and mechanism of electrochemical CO2 reduction have been explored on a model mesostructure of highly-ordered copper inverse opal (Cu-IO), which was fabricated by Cu electrodeposition in a hexagonally-closed packed polystyrene template. As the number of Cu-IO layers increases, the formation of C-2 products such as C2H4 and C2H5OH was significantly enhanced at reduced overpotentials (similar to 200 mV) compared to a planar Cu electrode. At the thickest layer, we observe for the first time the formation of acetylene (C2H2), which can be generated through a kinetically slow reaction pathway and be a key descriptor in the unveiling of the C-C coupling reaction mechanism. Based on our experimental observation, a plausible reaction pathway in Cu mesostructures is rationalized.

DOI： 10.1016/j.apcatb.2018.03.071

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Electrochemical conversion of CO2 has been considered as a promising method for producing value-added chemicals. Here, we report a systematic study on the formation of Au nanostructures via electroreduction of anodic Au(OH)(3) for selective CO production by an electrochemical CO2 reduction reaction (CO2RR). First, we demonstrate the influence of electrochemical process parameters on the formation of Au nanostructures and Au(OH)(3). The Au nanostructure morphologies can be tuned into either pore-like or pillar-like structures by controlling the anodic potential and/or reduction current density. This distinctive morphology is associated with the electric-field-assisted transport of Au3+ at/near the Au(OH)(3)/Au interface. Additionally, we report the catalytic activity of the morphology-controlled Au nanostructures in the CO2RR. Both Au nanostructures exhibit significantly higher CO selectivity at a low overpotential than the untreated Au film due to the high density of grain boundaries which can assist with faster stabilization of the CO2- intermediate. In particular, the pore-like structures have a higher CO selectivity than the pillar-like ones at 280 mV overpotential although the pillar-like Au nanostructures have a higher CO selectivity and CO producing current density at high overpotentials. This potential-dependent CO2RR performance of the two different Au nanostructures is discussed.

DOI： 10.1039/c8ta01010b

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Electrochemical CO2 reduction is one of the promising ways to convert CO, to value-added products such as CO. Many studies have dealt with suppressing the hydrogen evolution reaction (HER) and increasing the CO, reduction reaction (CO2RR) through modification of the metal surface with additives such as anchoring agent, anion, etc. However, there are only a few studies about modifying the Au surface with additives. We present here a theoretical prediction that the addition of the CN and Cl species on an Au electrode would enhance the electrochemical CO2RR due to van der Waals interactions with these large anionic species. On the basis of this suggestion, we then prepared functionalized Au electrodes by electroplating in an aqueous solution containing CN- or Cl- and experimentally verified that the CO2RR of functionalized Au indeed shows exceptional CO2RR activity in comparison to pristine Au.

DOI： 10.1021/acscatal.7b03449

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We report the effect of metal-oxide interfaces on CO oxidation catalytic activity with inverse TiO2-nano-structured Au catalysts. The inverse nanocatalysts were prepared by depositing TiO2 via the liquid-phase immersion method on electrochemically synthesized Au nanostructure supports. The catalytic performance for CO oxidation was investigated using various amounts of Ti (i.e. 0.1-1.0 wt%) on two different morphologies of Au nanostructures (i.e. nanoporous and nanorod). In comparing the different Au morphologies, we found an overall higher TOF and lower activation energy for the TiO2/nanoporous Au than those for the TiO2/nanorod Au. In addition, the CO oxidation activity increased as the Ti content increased up to 0.5 wt% probably due to active TiO2-Au interface sites enhancing CO oxidation via the supply of adsorption sites or charge transfer from TiO2 to Au. However, a higher titania content (i.e. 1.0 wt% TiO2) resulted in decreased activity caused by high surface coverage of TiO2 decreasing the number of TiO2 Au interface sites. These results implied that the perimeter area of the metal-oxide interface played a significant role in determining the catalytic performance for CO oxidation.

DOI： 10.1039/c7nr08168e

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Generating syngas (H-2 and CO mixture) from electrochemically reduced CO2 in an aqueous solution is one of the sustainable strategies utilizing atmospheric CO2 in value-added products. However, a conventional single-component metal catalyst, such as Ag, Au, or Zn, exhibits potential-dependent CO2 reduction selectivity, which could result in temporal variation of syngas composition and limit its use in large-scale electrochemical syngas production. Herein, we demonstrate the use of Ag nanowire (NW)/porous carbon sheet composite catalysts in the generation of syngas with tunable H-2/CO ratios having a large potential window to resist power fluctuation. These Ag NW/carbon sheet composite catalysts have a potential window increased by 10 times for generating syngas with the proper H-2/CO ratio (1.7-2.15) for the Fischer-Tropsch process and an increased syngas production rate of about 19 times compared to that of a Ag foil. Additionally, we tuned the H-2/CO ratio from similar to 2 to similar to 10 by adjusting only the quantity of the Ag NWs under the given electrode potential. We believe that our Ag NW/carbon sheet composite provides new possibilities for designing electrode structures with a large potential window and controlled CO2 reduction products in aqueous solutions.

DOI： 10.1021/acsomega.7b00846

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Molybdenum disulfide (MoS2) is an earth-abundant and low-cost hydrogen evolving electrocatalyst that can substitute noble metal catalysts. Atomic layer deposition (ALD) is a reliable and scalable process where MoS2 nanomaterials grow directly on Si with a precise film thickness and composition. Here, we demonstrate high-performance Si photocathodes with MoS2 cocatalysts using ALD for the photoelectrochemical (PEC) water reduction reaction. While the morphology and thickness of MoS2 is controlled by ALD reaction cycles, post-sulfurization at high temperatures is conducted to form stoichiometric MoS2 and dramatically enhances the crystallinity of MoS2 to maximize the catalytically active edge sites of basal planes. A systematic study was performed to investigate the role of ALD and post-sulfurization parameters on PEC performances of MoS2 on Si photocathodes. By optimizing the crystallinity, edge site density, stoichiometry, and morphology of MoS2 for maximum electrochemical HER performance and minimum optical and electrical losses, our Si photocathodes with ALD-MoS2 cocatalysts showed reduction of an overpotential of about 630 mV compared to bare Si. The photocathodes also showed a saturating photocurrent density of 31 mA cm(-2) without noticeable degradation during a 24 hour stability test in 0.5 M H2SO4 under a simulated 1 sun illumination.

DOI： 10.1039/c6ta10707a

記述言語：英語   掲載種別：研究論文（学術雑誌）  

An Si photoelectrode with a nanoporous Au thin film for highly selective and efficient photoelectrochemical (PEC) CO2 reduction reaction (CO2RR) is presented. The nanoporous Au thin film is formed by electrochemical reduction of an anodized Au thin film. The electrochemical treatments of the Au thin film critically improve CO2 reduction catalytic activity of Au catalysts and exhibit CO Faradaic efficiency of 96% at 480 mV of overpotential. To apply the electrochemical pretreatment of Au films for PEC CO2RR, a new Si photoelectrode design with mesh-type co-catalysts independently wired at the front and the back of the photoelectrode is demonstrated. Due to the superior CO2RR activity of the nanoporous Au mesh and high photovoltage from Si, the Si photoelectrode with the nanoporous Au thin film mesh shows conversion of CO2 to CO with 91% Faradaic efficiency at positive potential than the CO2/CO equilibrium potential.

DOI： 10.1002/aenm.201601103

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Photoelectrochemical (PEC) water splitting has emerged as a potential pathway to produce sustainable and renewable chemical fuels. Here, we present a highly active Cu2O/TiO2 photocathode for H-2 production by enhancing the interfacial band-edge energetics of the TiO2 layer, which is realized by controlling the fixed charge density of the TiO2 protection layer. The band-edge engineered Cu2O/TiO2 (where TiO2 was grown at 80 A degrees C via atomic layer deposition) enhances the photocurrent density up to -2.04 mA/cm(2) at 0 V vs. RHE under 1 sun illumination, corresponding to about a 1,200% enhancement compared to the photocurrent density of the photocathode protected with TiO2 grown at 150 A degrees C. Moreover, band-edge engineering of the TiO2 protection layer prevents electron accumulation at the TiO2 layer and enhances both the Faraday efficiency and the stability for hydrogen production during the PEC water reduction reaction. This facile control over the TiO2/electrolyte interface will also provide new insight for designing highly efficient and stable protection layers for various other photoelectrodes such as Si, InP, and GaAs.

DOI： 10.1007/s13391-017-6316-1

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Photoelectrochemical (PEC) carbon dioxide (CO2) reduction on a 3C-SiC photoanode is demonstrated in aqueous solution with Pt and Ag counter electrodes. It is demonstrated that 3C-SiC has sufficient potential for CO2 reduction by confirming the band-edge structure. Then, the CO2 reduction is realized by connecting the 3C-SiC photoanode with the counter electrode. As the products of the PEC reaction with an applied bias of 1V (vs counter electrode) to the 3C-SiC photoanode, hydrogen (H-2) and carbon monoxide (CO) were analyzed by highly sensitive micro-gas chromatography, by which the time dependence of the gas products can be analyzed. Under light illumination of the 3C-SiC photoanode, CO2 reduction occurred while producing 2.5 and 9 nmol of CO gas with the Pt and Ag counter electrodes, respectively, after the reaction for 3000 s. (C) 2015 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.54.04DR05

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The effect of Pt co-catalyst fabricated with various annealing temperatures on photoelectrochemical (PEC) properties of 3C-SiC photo-anode was investigated. 3C-SiC with Pt co-catalyst shows the greater PEC reaction compared with bare 3C-SiC. A further enhancement is found by annealing process due to the Pt particle structure and enhanced contact of 3C-SiC and Pt. The formation of Pt particles improves the PEC reaction of samples annealed at 500 and 700 degrees C. Here, 3C-SiC with the Pt annealed at 500 degrees C shows the largest photocurrent, 3.47mA/cm(2) at an applied bias of 1V (vs Ag/AgCl) and the lowest onset potential, 0.74V with the optimum particle size. It is also considered to have appropriate contact by the proper Pt2Si formation, revealed by X-ray photoelectron microscopy. Although photocurrent is improved after anneal at 700 degrees C, the onset potential becomes almost same as bare 3C-SiC. Furthermore, the photo-activity after anneal at 900 degrees C is even degraded compared to the bare 3C-SiC because of the evolution of immoderate carbon compounds suppressing Pt co-catalyst effect. (C) 2014 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.53.05FZ04

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We propose the n-type 3C-SiC with Pt nanoparticles (Pt NPs) as photo-anode for photoelectrochemical hydrogen (H-2) generation. We found that band-edge structure of 3C-SiC is suitable for H-2 generation, and the property can be optimized by dopant (nitrogen) concentration in 3C-SiC. We also confirmed that Pt NPs enhance photoelectrochemical properties showing 0.2%-0.8% higher Incident Photon-to-Current Efficiency than bare 3C-SiC in visible wavelength despite diminished light absorption. Solar-conversion efficiency increases approximately 6.3 times, and H-2 production is improved by 6.5 times with 33% of Faradaic efficiency. Lastly, 3C-SiC surface corrosion is effectively inhibited. (C) 2013 AIP Publishing LLC.

DOI： 10.1063/1.4832333

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, we proposed a square-patterned narrow-band infrared (IR) emitter for a filterless IR gas sensor. As a new method of infrared gas sensing compared with previous research, it is proposed that a narrow-band IR emitter fabricated by micro-electro-mechanical-systems (MEMS) technology be applied to analyze dimethyl ether [(CH3)(2)O] gas. The proposed IR emitter consists of a TiN/SiO2/TiN trilayer, where the top TiN layer is square-patterned. The IR emitter radiates emissions at wavelengths of 7.68 and 7.88 mu m in accordance with the type of sample. The wavelength can be adjusted by changing the period of the surface pattern. The proposed IR emitter shows a narrow peak width (Delta lambda/lambda) of 0.16-0.23. The apparatus for gas detection consists of the proposed IR emitter, a gas cell and a bolometric IR sensor based on amorphous SiGe:H. The change in electrical resistance of the gas detector during inflow of (CH3)(2)O gas, which has a fingerprint wavelength in the range of 7.6-10 mu m, was much smaller than that during inflow of CO2 gas, because (CH3)(2)O absorbed its corresponding wavelength in the range of 7.6-10 mu m. Because of the concentrated radiation of the IR emitter at the wavelength of 7.88 mu m, (CH3)(2)O absorbs relatively large amounts of infrared energy. The electrical resistance of the gas detector changed linearly as the concentration of (CH3)(2)O gas increased in the range of 0 to 500 ppm. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.51.06FL18

開催年月日： 2024年7月

記述言語：英語   会議種別：ポスター発表  

開催年月日： 2024年4月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：名古屋大学   国名：日本国  

開催年月日： 2024年4月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Gothenburg   国名：スウェーデン王国  

開催年月日： 2024年4月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Taipei   国名：台湾  

開催年月日： 2023年6月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：神奈川大学   国名：日本国  

開催年月日： 2023年5月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Seoul   国名：大韓民国  

開催年月日： 2023年5月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Seoul   国名：大韓民国  

開催年月日： 2022年6月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：オンライン   国名：日本国  

開催年月日： 2022年6月

記述言語：日本語  

開催地：オンライン   国名：日本国  

開催年月日： 2021年6月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：TBD   国名：大韓民国  

記述言語：英語  

開催地：Kirishima Spa and Resort Hotel   国名：日本国  

記述言語：日本語  

開催地：九州大学筑紫キャンパス   国名：日本国  

種別：査読等 

外国語雑誌　査読論文数：3

種別：査読等 

外国語雑誌　査読論文数：8