Language：English   Publisher：Physical Chemistry Chemical Physics  

Acceptor-substituted Ba(Zr,Ce)O<inf>3</inf> proton conducting oxides have attracted significant attention due to their excellent proton conductivity at intermediate temperatures (400-600 °C). A high Zr/Ce ratio is crucial for maintaining stability in humid or other harsh atmospheres. Herein, a systematic study was conducted on the phase composition, microstructure, and the resulting hydration ability and electrochemical performance of high Zr/Ce ratio Ba(Zr,Ce)O<inf>3</inf> solid solutions with different Y substitution levels (10 at% to 30 at%). In this substitution range, no apparent secondary phase can be found from XRD, leading to a continuous increase in hydration content. A Y-rich phase was observed in SEM for compositions with high levels of Y substitution. The impact of Y on proton conduction was examined using EIS, with particular attention on elucidating the effects of varying amounts of Y on bulk proton conduction. The increase of proton conductivity was primarily due to the increased charge carrier (proton) concentration caused by Y substitution. Different concentrations of Y have little effect on proton mobility, indicating a compromise between different mechanisms such as the Y trapping effect and the nano-percolation effect. Grain boundary proton conduction was discussed combining the TEM-EDS results to explain the space charge layer effect. Mechanical properties and thermo-chemical stability were also considered to pave the way for real applications.

DOI： 10.1039/d4cp04384g

Scopus

PubMed

Publisher：Microchemical Journal  

The growing reliance on nuclear energy and uncharacteristic accidents, such as those in Chornobyl and Fukushima, have emphasized the need for effective radiocesium (r-Cs: ¹³⁷Cs) removal from environmental wastewater. This study presents the development of DFDB18C6@SBA-NH<inf>2</inf>, a novel solid-phase sorbent designed to remove r-Cs from aqueous environments selectively. The sorbent was synthesized by tethering a macrocyclic ligand, DFDB18C6 (di-formyl dibenzo-18-crown-6-ether), to amino-functionalized mesoporous SBA-15 (Santa Barbara Amorphous-15). The sorbent's structure, thermal properties, and surface morphology were comprehensively characterized. Batch sorption experiments were performed to evaluate the influence of different operating factors on r-Cs sorption, including solution pH, contact duration, initial ion concentration, ambient temperature, and matrix ions contents. The sorption behavior was better explained with the pseudo-second-order kinetic and Langmuir isotherm models, which suggest a probable monolayer chemisorption process. The thermodynamic evaluation indicated the exothermic nature of the sorption process. The DFDB18C6@SBA-NH<inf>2</inf> sorbent demonstrated significant ¹³⁷Cs removal (approximately 85 %) from Fukushima-originated wastewater, with competing matrix ions such as Ca²⁺, Mg²⁺, Na⁺, and K⁺. These results highlight the potential of DFDB18C6@SBA-NH<inf>2</inf> as a potential solid-phase sorbent for efficient and selective r-Cs decontamination in waste aqueous matrices.

DOI： 10.1016/j.microc.2024.111649

Scopus

Publisher：Solid State Ionics  

Direct production of pressurized hydrogen through polymer exchange membrane (PEM) water electrolysis without the usage of the external compressor is an industrially important approach to maximize energy efficiency. An additional challenge in conventional water electrolyzers is the lack of separation of the generated gases, hydrogen and oxygen, from water. In this report, we demonstrate the operation of a new water electrolysis cell at high inlet water pressure with the assistance of a hydrophobic gas diffusion layer (hydrophobic-GDL). This configuration allows the gas/water separation to take place at the electrode so that pressurized water-free gases can be the output due to water being injected directly into the membrane as a source of electrolysis for a continuous supply of water it prevents membrane dehydration. Another important feature is also the cell can be operable in a reversible operation by combining with fuel cell operation. The membrane electrode assemblies (MEAs) were prepared using the hydrophobic-GDL, a Nafion membrane, and Pt-C/IrO<inf>2</inf> catalysts. Electrolysis experiments were performed at different temperatures with pressurized water (ΔP = 0.05–0.4 MPa based on atmospheric pressure) resulting output was pressurized (0.05–0.4 MPa) hydrogen and oxygen gases. The current densities at 1.6 V of electrolysis voltage were 117, 188, 262 mA cm⁻² at 25, 60, and 80 °C, respectively, and the hydrogen and oxygen gas evolution rates were consistent with theoretical values. It was found that increasing water pressure is beneficial to the electrode kinetics and there was an increase in water transport to the electrode surface as well as efficient gas separation and the production of pressurized gases.

DOI： 10.1016/j.ssi.2024.116678

Web of Science

Scopus

Publisher：Solid State Ionics  

Solid oxide protonic fuel cells are one of the most efficient means of directly converting stored chemical energy to usable electrical energy. Acceptor-doped Ba(Zr, Ce)O<inf>3</inf> perovskite-type oxides are the preferred electrolyte choice as they provide higher conductivity due to lower activation energy. While substantial progress has been made on small-sized protonic laboratory-scale cells, a considerable challenge has been upscaling robust planar-type devices. This paper employs a cost-effective inverse tape casting route and screen printing to fabricate flat planar anode-supported protonic fuel cells consisting of NiO-SrZr<inf>0.5</inf>Ce<inf>0.4</inf>Y<inf>0.1</inf>O<inf>3-δ</inf> substrate, SrZr<inf>0.5</inf>Ce<inf>0.4</inf>Y<inf>0.1</inf>O<inf>3-δ</inf> electrolyte, and BaCo<inf>0.4</inf>Fe<inf>0.4</inf>Zr<inf>0.1</inf>Y <inf>0.1</inf>O<inf>3-δ</inf> as the cathode. The processing parameters were analyzed and adjusted to obtain defect-free single cells of dimension up to 100 mm × 100 mm × 0.5 mm with diminished warping. In addition, the smooth tri-layered green tapes yielded suitably dense and gas-tight electrolyte layers after co-sintering at 1300 °C/5 h. Finally, the electrochemical performance of the 50 × 50 mm² SrZr<inf>0.5</inf>Ce<inf>0.4</inf>Y<inf>0.1</inf>O<inf>2.95</inf> based cells was evaluated, and their impedance spectra were deconvoluted to identify all performance-related polarization processes via the distribution of relaxation time.

DOI： 10.1016/j.ssi.2022.115918

Scopus

Publisher：Wiley  

<jats:title>Abstract</jats:title><jats:p>Acceptor‐doped barium zirconate cerate electrolytes constitute prospective materials for highly efficient and environmentally friendly electrochemical devices. This manuscript employs a systematic approach to further optimize ionic conductivity in Ba(Zr<jats:sub><jats:italic>x</jats:italic></jats:sub>Ce<jats:sub>10−<jats:italic>x</jats:italic></jats:sub>)<jats:sub>0.08</jats:sub>Y<jats:sub>0.2</jats:sub>O<jats:sub>3−δ</jats:sub>, (1≤x≤9) oxides for moderate temperature electrolysis. We found two new composition variants by fixing a cerium/zirconium ratio of 5/4 at the perovskite B‐site with incremental zirconium, an observation that contrasts many reports suggesting a linear decrease in conductivity with increasing zirconium. As a result, the composition BaZr<jats:sub>0.44</jats:sub>Ce<jats:sub>0.36</jats:sub>Y<jats:sub>0.2</jats:sub>O<jats:sub>3−δ</jats:sub> demonstrates a superior ionic conductivity (10.1 mS cm<jats:sup>−1</jats:sup> at 500 °C) to stability trade‐off whereas, BaZr<jats:sub>0.16</jats:sub>Ce<jats:sub>0.64</jats:sub>Y<jats:sub>0.2</jats:sub>O<jats:sub>3−δ</jats:sub> exhibits the highest conductivity (11.5 mS cm<jats:sup>−1</jats:sup> at 500 °C) among the studied pellets. The high protonic conductivity is associated with a high degree of hydration, as confirmed by thermo‐gravimetric analysis. In addition, both compositions as electrolytes allow successful hydrogen production in a steam electrolyzer prototype. Electrolysis voltage as low as 1.3 V is attainable at current densities of 600 and 500 mA/cm<jats:sup>2</jats:sup> respectively at 600 °C, achieving 82 % current efficiencies with the later electrolyte.</jats:p>

DOI： 10.1002/celc.202101663

Scopus

CiNii Research

Publisher：Bulletin of the Chemical Society of Japan  

Current greenhouse gas emissions suggest that keeping global temperature increase below 1.5 degrees, as espoused in the Paris Agreements will be challenging, and to do so, the achievement of carbon neutrality is of utmost importance. It is also clear that no single solution can meet the carbon neutral challenge, so it is essential for scientific research to cover a broad range of technologies and initiatives which will enable the realization of a carbon free energy system. This study details the broad, yet targeted research themes being pioneered within the International Institute for Carbon-Neutral Energy Research (I2CNER). These approaches include hydrogen materials, bio-mimetic catalysts, electrochemistry, thermal energy and absorption, carbon capture, storage and management and refrigerants. Here we outline the state of the art for this suite of technologies and detail how their deployment, alongside prudent energy policy implementation can engender a carbon neutral Japan by 2050. Recognizing that just as no single technological solution will engender carbon neutrality, no single nation can expect to achieve this goal alone. This study represents a recognition of conducive international policy agendas and is representative of interdisciplinary, international collaboration.

DOI： 10.1246/bcsj.20210323

Web of Science

Scopus

Publisher：Royal Society of Chemistry (RSC)  

<jats:p>This work focuses on understanding the oxygen-ion transport through the mixed Grain Boundaries (GBs) present in yttria-stabilized zirconia (YSZ), a common solid oxide fuel cells (SOFCs) electrolyte.</jats:p>

DOI： 10.1039/d1ta08309k

Scopus

CiNii Research