記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/C4CY00660G

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10562-014-1316-3

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.colsurfa.2014.04.056

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.jcat.2013.05.016

記述言語：英語  

DOI： 10.1016/j.apcatb.2013.05.041

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/catal3010219

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）  

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）  

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）  

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）  

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）  

記述言語：日本語   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）  

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）  

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）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.cattod.2014.05.018

出版者・発行元：Chemical Engineering Journal  

The bio-based production of essential chemicals is important for the sustainability of the chemical industry. Here, we demonstrate efficient olefin production from methyl oleate using Na substituted ZSM-5 (Na-ZSM-5) and microwave irradiation. Na-ZSM-5 exhibits superior microwave heating properties compared to H-ZSM-5 and other zeolites. It was more effective in converting methyl oleate to olefins such as ethylene and propylene than H-ZSM-5 or Y zeolites. Microwave irradiation promoted the conversion efficiency of methyl oleate by Na-ZSM-5, achieving an olefin yield over four times higher than that obtained with conventional heating (CH) using an electric furnace. Meanwhile, the aromatization to benzene, toluene and xylene (BTX) was suppressed using Na-ZSM-5, which was attributed to the removal of strong acid sites. In addition, in situ microwave XRD revealed that microwaves promoted temperature-dependent structural changes in Na-ZSM-5 at lower temperatures than CH, suggesting that microwaves form localized high temperatures in the zeolite. These localized high temperatures effectively enhance olefin production via microwave irradiation.

DOI： 10.1016/j.cej.2024.154737

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出版者・発行元：Catalysts  

Transition metal oxides show high activity while still facing the challenges of low mineralization and poor durability in the ozone catalytic oxidation (OCO) of volatile organic compounds (VOCs). Improving the oxygen mobility and low-temperature reducibility of transition metal oxides was found to be an effective way to address the above challenges. Here, highly dispersed Ag was added to Mn3O4 via the co-precipitation oxalate route, and the obtained Ag/Mn3O4 exhibited higher mineralization and stability in benzene catalytic ozonation at room temperature. Compared to Mn3O4, the concentration of CO2 formed from benzene oxidation over Ag/Mn3O4 was significantly increased, from 585.4 ppm to 810.9 ppm, while CO generation was greatly suppressed to only one tenth of its original value (194 ppm vs. 19 ppm). In addition, Ag/Mn3O4 exhibited higher catalytic stability than Mn3O4. The introduction of Ag obviously improved the oxygen mobility and low-temperature reducibility of Mn3O4. Moreover, the highly dispersed Ag also promoted the activity of surface oxygen species and the chemisorption of benzene on Mn3O4. The above physicochemical properties contributed to the excellent catalytic performance and durability of Ag/Mn3O4. This research could shed light on the improvement in VOC mineralization via ozone catalytic oxidation.

DOI： 10.3390/catal14090554

Scopus

出版者・発行元：Journal of Physical Chemistry C  

Microwave heating is an effective method for efficiently heating a target material, allowing the chemical reaction processes to proceed quickly. In catalytic reactions under microwave irradiation, it is essential to understand the relationship between the structure and physical properties of the material to be used as a catalyst and microwave heating. In this study, we focused on tungsten oxides, which absorb microwaves and convert them into heat, and we compared the microwave heating properties of tungsten oxides with different structures. The heating properties of tungsten oxides under microwave irradiation are highly dependent on their morphologies. WO3 nanoflakes with a monoclinic phase structure have a more rapidly heated surface than tungsten oxides with other morphologies. The heating characteristics of each tungsten oxide were consistent with the dielectric loss factor obtained by the perturbation method. Finite element analysis was used to gain a better understanding of the thermal distribution of materials during microwave irradiation.

DOI： 10.1021/acs.jpcc.4c02936

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記述言語：英語   出版者・発行元：Environmental Science and Pollution Research  

The development of technologies for highly efficient treatment of emissions containing low concentrations of volatile organic compounds (VOCs) remains an important challenge. Catalytic oxidation with ozone (catalytic ozonation) is useful for the oxidative decomposition of VOCs, particularly aromatic compounds, under ambient temperature conditions. Only inexpensive transition metal oxides are required as catalysts, and Mn-based catalysts are widely used for catalytic ozonation. This review describes the oxidation reaction mechanisms, reaction pathways of aromatic hydrocarbons, and dependence of the catalytic ozonation activity on the reaction conditions. The reasons why Mn oxides are effective in catalytic ozonation are also explained. The structure of the catalytic active sites and the types of supporting materials contributing to the reaction are also discussed in detail, with the aim of establishing a VOC control technology. In addition, recent progress in catalytic oxidation processes using ozone as an oxidant has been outlined, focusing on catalyst materials and reaction conditions.

DOI： 10.1007/s11356-024-34004-3

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PubMed

出版者・発行元：Journal of the Taiwan Institute of Chemical Engineers  

Microwave-assisted catalytic reactions have been investigated for energy-efficient chemical processes. However, catalysts with comparatively high heating properties, activities, and economics have been developed with limited success. In this study, we investigated the catalytic properties of Ce addition to LaNiO3 catalyst, which has high CO oxidation activity and high microwave heating properties. Ce-added catalysts exhibited high heating properties under microwave heating. Increasing the Ce content in the catalyst enhanced the dielectric loss factor, the ability to absorb microwaves and convert them to heat, and improved the microwave heating properties of the catalyst. The catalytic activity toward CO oxidation over Ce-added catalysts decreased in the order of La0.8Ce0.2NiO3 > La0.9Ce0.1NiO3 > LaNiO3 at all oxygen partial pressures when compared to the same microwave power. To clarify the role of Ce addition, temperature programmed reduction (TPR) by H2, CO, and XAFS measurements were performed. TPR results suggested that Ce promotes oxygen mobility and then affects both CO oxidation and microwave heating properties.

DOI： 10.1016/j.jtice.2023.105041

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出版者・発行元：Applied Catalysis A: General  

In this work, Mn-Ni solid solutions were obtained by doping Ni into MnOx via solution combustion synthesis and the resulting catalysts were then applied to benzene oxidation. Various characterizations revealed that Ni doping changed the metal oxygen bond parameters, such as coordination numbers (CNs) and bond length. Both Mn-O and Ni-O bonds in Mn-Ni solid solutions exerted reduced CNs, while the bond length of Mn-O bonds was extended, making the oxygen species more chemically reactive., which further improved physicochemical properties (such as reducibility, oxygen mobility, surface active oxygen species etc.) and catalytic performance. Remarkably, the solid solutions with a Mn/Ni molar ratio of 4:1 (named Mn4Ni1) showed Mn-O and Ni-O bonds with lower CNs and longer bond lengths, which enhanced the activity and mobility of oxygen species, reducibility and chemisorption capacity of benzene. Therefore, Mn4Ni1 demonstrated optimal benzene oxidation activity and showed the lowest T90 (192 °C). The potential reaction mechanism was proposed according to the analysis results of C6H6-TPSR and in-situ FTIR. Furthermore, promoted oxidation of benzene and phenolate species on Mn4Ni1 could inhibit accumulation of intermediates and avoid catalyst poisoning and deactivation. This strategy shed light to the design of catalysts in environmental catalysis and thermal catalysis.

DOI： 10.1016/j.apcata.2024.119575

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記述言語：英語   出版者・発行元：ACS Nano  

The interaction between a metal and a support, which is known as the metal-support interaction, often plays a determining role in the catalytic properties of supported metal catalysts. Herein, we have developed model Pt/CeO2 catalysts, which enabled us to investigate the interface atomic and electronic structures between Pt and the {001}, {011}, and {111} planes of CeO2 using scanning transmission electron microscopy and electron energy-loss spectroscopy. We found that the number of Ce3+ ions around the Pt nanoparticles followed the order {001} > {011} > {111}, which was the opposite order of the generally accepted stability of low index surfaces of CeO2. Systematic first-principles calculations revealed that the presence of Pt nanoparticles facilitated the formation of oxygen vacancies and that the appearance of the Ptδ+ state was preferred when Pt nanoparticles were in contact with CeO2 {001} planes due to direct charge transfer from Pt to CeO2. These results provide important insights into the nature of the metal-support interaction for a comprehensive understanding of the properties of supported metal catalysts.

DOI： 10.1021/acsnano.3c09092

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PubMed

出版者・発行元：ChemCatChem  

Selective oxidation reactions are crucial in producing various chemicals in the industry. However, most catalytic processes for these reactions use harsh reaction conditions. Recently, heterogeneous photo(electro)catalysis has been considered promising for selective oxidation reactions under mild conditions. Semiconductor materials are frequently used as heterogeneous photocatalysts because they can produce active species that contribute to the oxidation of organic compounds under light irradiation. Among various semiconductor photocatalysts, tungsten oxide (WO3) is one of the most promising candidates due to its advantages, including high stability, wide light adsorption range, proper band structures, and unique catalytic mechanism. This paper reviews the WO3-based materials for photocatalytic (PC) and photoelectrocatalytic (PEC) selective oxidations. We summarize the strategies for designing WO3 structures, which include morphology control, crystal facet optimization, and defect engineering. Then, the finely designed WO3 structures for PC and PEC oxidation of several typical organic compounds have been discussed based on catalytic mechanism and performance. Finally, we propose the prospects and challenges of WO3 photocatalysts and photoanodes in selective oxidation reactions.

DOI： 10.1002/cctc.202300723

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出版者・発行元：Catalysis Letters  

The effect of sulfurization by SO2 on the activity of Pd/γ-Al2O3 for benzene oxidation was investigated. The activity decreased by heat treatment at 800 °C due to Pd particle coarsening. SO2 treatment at 600 °C suppressed the formation of byproduct compounds on the catalyst and improved the activity of the sintered Pd/γ-Al2O3 catalyst. Graphical Abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s10562-022-04233-7

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記述言語：英語   出版者・発行元：Journal of Environmental Sciences (China)  

Non-thermal plasma (NTP) has been demonstrated as one of the promising technologies that can degrade volatile organic compounds (VOCs) under ambient condition. However, one of the key challenges of VOCs degradation in NTP is its relatively low mineralization rate, which needs to be addressed by introducing catalysts. Therefore, the design and optimization of catalysts have become the focus of NTP coupling catalysis research. In this work, a series of two-dimensional nanosheet Co-Ni metal oxides were synthesized by microwave method and investigated for the catalytic oxidation of benzene in an NTP-catalysis coupling system. Among them, Co2Ni1Ox achieves 60% carbon dioxide (CO2) selectivity (SCO2) when the benzene removal efficiency (REbenzene) reaches more than 99%, which is a significant enhancement compared with the CO2 selectivity obtained without any catalysts (38%) under the same input power. More intriguingly, this SCO2 is also significantly higher than that of single metal oxides, NiO or Co3O4, which is only around 40%. Such improved performance of this binary metal oxide catalyst is uniquely attributed to the synergistic effects of Co and Ni in Co2Ni1Ox catalyst. The introduction of Co2Ni1Ox was found to promote the generation of acrolein significantly, one of the key intermediates found in NTP alone system reported previously, suggest the benzene ring open reaction is promoted. Compared with monometallic oxides NiO and Co3O4, Co2Ni1Ox also shows higher active oxygen proportion, better oxygen mobility, and stronger low-temperature redox capability. The above factors result in the improved catalytic performance of Co2Ni1Ox in the NTP coupling removal of benzene.

DOI： 10.1016/j.jes.2022.09.030

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PubMed

記述言語：英語   出版者・発行元：Dalton Transactions  

Phenol is an important intermediate for manufacturing chemical products in industry. In recent decades, phenol synthesis by one-pot oxidation of benzene has aroused tremendous interest in phenol synthesis due to the enormous energy consumption of the three-step cumene method in the industry. Photocatalysis is promising for the selective conversion of benzene to phenol because it can proceed under mild reaction conditions. However, overoxidation of phenol by photocatalysts with high oxidation ability decreases the yield and selectivity, which is the major limiting factor. Thus, increasing the phenol formation efficiency plays a crucial role in photocatalytic systems for benzene oxidation. In this context, selective photocatalytic benzene oxidation over several types of photocatalytic systems has been developed rapidly in the past few years. In this perspective, current homogeneous and heterogeneous photocatalytic systems for this reaction have been reviewed systematically first. Then, an overview of some strategies from the last decade for increasing phenol selectivity has been provided. In the end, a summary and outlook on the challenges and future directions in the research field are included in this perspective, which would be of great interest for further improving the selectivity of the photocatalytic benzene oxidation reaction.

DOI： 10.1039/d3dt01360j

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PubMed

出版者・発行元：Applied Catalysis B: Environmental  

Co-substituted Cu-Mn spinel oxides were synthesized, characterized, and catalytic performance for benzene oxidation was evaluated. Spinel phases, and the substitution of Mn sites by Co were confirmed for the ternary oxides. Co0.2Cu0.8MnOy showed the highest activities with the lowest apparent activation energy among the ternary oxides. The improved catalytic properties due to Co substitution are attributed to more activated lattice oxygen, stronger adsorption of benzene, and a larger specific surface area. Density functional theory simulations also revealed that the Co substitution enhanced the reactivity of the lattice oxygen. Adsorbed and activated benzene reacted with lattice oxygen to form abundant oxygen defects, which promoted O2 adsorption and dissociation, contributing to enhanced catalytic activity. The effect of water vapor on the catalytic benzene oxidation was also clarified.

DOI： 10.1016/j.apcatb.2022.122099

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記述言語：英語   出版者・発行元：Wiley  

CeO2 and CeO2-based materials are widely used as catalysts and catalyst supports for a variety of chemical reactions. The ability to form oxygen vacancies plays an important role in the catalytic activities in these materials. Therefore, revealing the reduction mechanism for CeO2 is crucial to understanding the catalytic activities. In this study, shape-controlled CeO2 nanoparticles are fabricated and the distribution of surface oxygen vacancies on the (100) and (111) surfaces is systematically studied using scanning transmission electron microscopy and electron energy-loss spectroscopy and the response to H2 reduction treatment. It is successfully demonstrated that both catalytic activities and the ability to form oxygen vacancies are strongly dependent on the type of lattice planes. Moreover, the present results provide important insights into the reduction mechanism for CeO2, in which bulk oxygen instead of the widely believed surface capping oxygen makes no small contribution to the initial reduction step.

DOI： 10.1002/admi.202201954

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CiNii Research

出版者・発行元：Catalysis Today  

ABO3-type perovskite oxides containing transition metals at the B site are effective catalysts for oxidation reactions. In this study, LaNiO3 was prepared by the hydrolysis-precipitation method, and LaNiO3 was modified with Mn by the impregnation method. LaNiO3 showed higher CO oxidation activity than LaCoO3, LaMnO3, and LaFeO3. The high activity of LaNiO3 was attributed to the reactivity of the lattice oxygen in LaNiO3, as confirmed by temperature-programmed reduction by H2 (H2-TPR) and CO-TPR studies. The Mn-modified LaNiO3 exhibited higher activity for benzene oxidation than LaNiO3. The CO oxidation properties of the Mn-modified LaNiO3 catalysts correlated with their H2-reduction properties, whereas benzene oxidation properties were improved by the increasing amount of Mn on the catalyst surface.

DOI： 10.1016/j.cattod.2022.07.002

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出版者・発行元：ACS Catalysis  

The photocatalytic oxidation of benzene to phenol driven by visible light (λ > 420 nm) at room temperature and under ambient pressure is a promising process. In particular, the application of heterogeneous catalysts to benzene photooxidation, where the catalyst and product are easily separated, facilitates the construction of practical processes. Here, we report that a Pt-loaded 1D monoclinic WO3nanorod (Pt/m-WNR) exhibited higher activities than other Pt/WO3catalysts with different crystal structures and morphologies in water under ambient conditions and visible light. Pt/m-WNR showed high stability in repeated reactions. Furthermore, other typical photocatalysts (TiO2, Bi2WO6, Bi2MoO6, BiOBr, and C3N4) showed negligible phenol formation using Pt as a cocatalyst. Both experimental results and density functional theory calculations show that the specific performance of Pt/m-WNR is due to the efficient reduction of O2to produce hydroxyl radicals via H2O2as an intermediate. Notably, m-WNR shows much higher phenol formation than h-WNR, although h-WNR has a higher surface area. The higher activity of m-WNR may be due to its lower work function to provide electrons for O2reduction. A lower work function will favorably form a higher Schottky barrier with Pt nanoparticles to suppress the recombination of photogenerated charge carriers. The effect of the Schottky barrier is further confirmed by different activities using various metal particles as cocatalysts.

DOI： 10.1021/acscatal.2c03832

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出版者・発行元：Industrial and Engineering Chemistry Research  

Catalytic CO oxidation processes under dilute oxygen conditions are key industrial and environmental processes. CeO2-supported Pd and Pd-Cu catalysts (Pd/CeO2and Pd-Cu/CeO2) were prepared by impregnation, and the effect of Cu addition on the catalytic properties of CO oxidation was investigated under CO/O2stoichiometric conditions. The activity of Pd/CeO2was superior to that of Pd/TiO2and Pd/Al2O3at low temperatures. The Cu addition to Pd/CeO2with a Cu/Pd molar ratio of approximately 1-5 enhanced the CO oxidation activity. Small PdO particles were distributed over the CeO2surfaces, and Cu addition decreased the size of the Pd particles on the CeO2and increased the fraction of highly reactive Pd sites. As the Cu/Pd mole fraction in the Pd-Cu/CeO2catalyst increased to 10, the PdO on CeO2agglomerated significantly, and the CO oxidation activity decreased.

DOI： 10.1021/acs.iecr.2c02199

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記述言語：英語   出版者・発行元：Science  

A goal in the characterization of supported metal catalysts is to achieve particle-by-particle analysis of the charge state strongly correlated with the catalytic activity. Here, we demonstrate the direct identification of the charge state of individual platinum nanoparticles (NPs) supported on titanium dioxide using ultrahigh sensitivity and precision electron holography. Sophisticated phase-shift analysis for the part of the NPs protruding into the vacuum visualized slight potential changes around individual platinum NPs. The analysis revealed the number (only one to six electrons) and sense (positive or negative) of the charge per platinum NP. The underlying mechanism of platinum charging is explained by the work function differences between platinum and titanium dioxide (depending on the orientation relationship and lattice distortion) and by first-principles calculations in terms of the charge transfer processes.

DOI： 10.1126/science.abq5868

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PubMed

出版者・発行元：Journal of Environmental Chemical Engineering  

Microwave-assisted process has been demonstrated to have immense potential for promoting chemical reactions and reducing energy consumption. In this study, catalytic oxidation of benzene was carried out over Co-Cu-Mn mixed oxides (CoxMn1-xCuOy) under microwave irradiation. The spinel-type mixed oxides were mainly formed for the Co-Cu-Mn mixed oxides with different Co/Mn ratios. The substitution of Mn sites by Co was confirmed by Fourier and Wavelet transformed extended x-ray absorption fine structure spectra. As the Co/Mn ratio increased, the heating characteristics of the catalysts under microwave irradiation monotonically improved. The benzene oxidation activity increased on the Co/Mn ratio of 2/3 due to the enhanced specific surface area, benzene adsorption properties, and lattice-oxygen reactivity. Microwave inducing significantly lowered the reaction temperature required for benzene oxidation. Co0.4Mn0.6CuOy completely oxidized benzene at a relatively low microwave power compared to pristine Cu-Mn oxides. The Co-Cu-Mn oxides showed high activity and stability for benzene oxidation even under humid conditions. Combining pre-adsorption and thermal oxidation processes on Co0.4Mn0.6CuOy improved the low concentration of benzene oxidation efficiency by rapid microwave heating. The compound of Co0.4Mn0.6CuOy and Co0.8Mn0.2CuOy mixed at 3:1 showed even higher activity than Co0.4Mn0.6CuOy.

DOI： 10.1016/j.jece.2022.108212

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出版者・発行元：ACS Sustainable Chemistry and Engineering  

Catalytic hydrogenolysis is an efficient method for converting lignin-derived aryl ethers into monoaromatic products by cleaving the C-O bond and maintaining the phenyl rings. However, it is difficult to obtain aromatics with high selectivity because ring hydrogenation proceeds in parallel. Herein, we showed that a Cl-modified Pt/γ-Al2O3 catalyst exhibited higher selectivity for aromatics (91.6%) compared to unmodified Pt/γ-Al2O3 (3.9%) in C-O bond cleavage of diphenyl ether (DPE, 4-O-5 linkage in lignin). Characterization of the catalysts and density functional theory (DFT) calculations indicated that the Cl species preferred to localize at the terrace sites of Pt nanoparticles (NPs). Due to the decrease in the number of active sites, the Cl-modified Pt/γ-Al2O3 catalyst exhibited low activity for 2-propanol dehydrogenation, and thus the catalytic activity for the hydrogenation of aromatic products was suppressed. On the other hand, DPE adsorbed at the low coordination site, which caused the phenyl rings to move away from the metal surface; this configuration was unfavorable for the hydrogenation reaction. According to DFT calculations, the high selectivity for benzene was mainly attributed to the lower energy barrier for C-O bond cleavage of phenol at the low-coordination sites.

DOI： 10.1021/acssuschemeng.2c02038

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記述言語：英語   出版者・発行元：Environmental Science and Technology  

The Co3O4spinel is one of the most promising transition metal oxide (TMO) catalysts for volatile organic compound (VOC) treatment. Substituting effects have usually been utilized to improve the catalytic performance of the Co3O4spinel. In this study, Cu- and Ni-substituted Co3O4catalysts derived from mixed metal-organic frameworks (MMOFs) retained similar spinel structures but exhibited improved and reduced performance for o-xylene oxidation, respectively. Physicochemical characterization and DFT calculations revealed that Cu and Ni substitution into the Co3O4spinel varied the valence (Co3+/Co2+) and geometry (CoOh/CoTd) distributions of Co cations through different partial electron transfer and substitution sites. The higher Co3+/Co2+and CoOh/CoTdratios of the CuCo2O4catalyst contributed to the superior reducibility and oxygen mobility, which facilitated the oxidation of intermediates at lower temperatures in the catalytic oxidation of o-xylene. Meanwhile, the NiCo2O4catalyst with lower Co3+/Co2+and CoOh/CoTdratios could not completely oxidize intermediates under the same conditions due to inferior redox properties. Therefore, the CuCo2O4catalyst showed superior catalytic activity and stability to the NiCo2O4catalyst for the catalytic oxidation of o-xylene. This work provides insights into the synthesis of substituted Co3O4catalysts from MMOFs and mechanism of substituting effects, which might guide the design of efficient TMO catalysts for VOC treatment.

DOI： 10.1021/acs.est.2c02450

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PubMed

出版者・発行元：ACS Applied Energy Materials  

Photocatalytic reactions to produce hydrogen from water under visible-light irradiation are an important key process for solar energy utilization. Because Cu-doped ZnS undergoes redox reactions upon irradiation with visible light, these materials have been applied to hydrogen production. In this study, Cu-doped ZnS catalysts were prepared by a solvothermal method, and their structures were investigated using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and ultraviolet-visible spectroscopic studies. Cu-doped ZnS consists of nanospherical particles with a diameter of 50 nm. Cu2+ doping in ZnS causes structural distortion of the ZnS. The local structures were analyzed by X-ray absorption fine structure studies. As the amount of Cu added to ZnS increased, the degree of distortion of the ZnS structure also increased, and this degree of distortion reached a maximum when the Cu/Zn ratio was 0.07 (7% Cu doping). Cu-doped ZnS exhibited high activity in the hydrogen production reaction from water using Na2S and Na2SO3 as sacrificial agents under visible-light irradiation (λ > 420 nm), and the highest activity was observed at 7% Cu doping.

DOI： 10.1021/acsaem.1c03323

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記述言語：英語   出版者・発行元：Journal of Hazardous Materials  

Microwave-assisted heterogeneous catalytic oxidation of benzene was investigated over Cu-Mn spinel oxides. The spinel oxides were synthesized by a coprecipitation method from metal nitrate hydrolysis in a solution using tetramethylammonium hydroxide (TMAH) as a precipitation reagent. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption fine structure, scanning electron microscopy, transmission electron microscope and H2-temperature-programmed reduction studies. Microwave absorption by the Cu-Mn spinel oxide is mainly driven by dielectric losses (dielectric heating). Cu-Mn spinel oxide with a Cu/Mn ratio of 1 exhibited superior activity to single oxides under microwave heating, demonstrating lower apparent activation energy than that obtained under conventional heating. Microwave irradiation lowered the reaction temperature required for benzene oxidation compared with conventional heating. Transient tests were used to investigate the reactivity of oxygen species in the catalytic reaction, and the high reactivity of Cu-Mn spinel oxides was related to the high reactivity of lattice oxygen on the catalyst surface. The reactivity of the oxygen species was enhanced under microwave heating, leading to an enhanced benzene oxidation reaction. The combination of adsorption and catalytic oxidation processes using Cu-Mn spinel oxides and zeolites efficiently decomposed benzene at low concentrations.

DOI： 10.1016/j.jhazmat.2021.127523

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PubMed

出版者・発行元：Applied Physics Letters  

To enable better statistical analysis of catalyst nanoparticles by high-resolution electron holography, we improved the particle detection accuracy of our previously developed automated hologram acquisition system by using an image classifier trained with machine learning. The detection accuracy of 83% was achieved with the small training data of just 232 images showing nanoparticles by utilizing transfer learning based on VGG16 to train the image classifier. Although the construction of training data generally requires much effort, the time needed to select the training data candidates was significantly shortened by utilizing a pattern matching technique. Experimental results showed that the high-resolution hologram acquisition efficiency was improved by factors of about 100 and 6 compared to a scan method and a pattern-matching-only method, respectively.

DOI： 10.1063/5.0074231

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記述言語：日本語   出版者・発行元：一般社団法人 日本エネルギー学会  

DOI： 10.20550/jiebiomassronbun.17.0_29

CiNii Research

記述言語：英語   出版者・発行元：Nano Letters  

Understanding the nature of the interaction between a metal and support, which is known as the metal–support interaction, in supported metal catalysts is crucial to design catalysts with desired properties. Here, we have developed model Pt/TiO2 catalysts based on the deposition of colloidal Pt nanoparticles and studied their atomic and electronic structures before and after a postdeposition treatment that induces catalytic activity using aberration-corrected scanning transmission electron microscopy, electron energy loss spectroscopy, and first-principles calculations. Direct contact between Pt nanoparticles and TiO2 is realized after the postdeposition treatment, which is accompanied by the formation of a Ti3+ state on the TiO2 surface close to the Pt nanoparticles and a Ptδ+ state on the Pt nanoparticles. The origin of these two states and their effect on the catalytic properties are discussed. These findings pave the way for a comprehensive understanding of metal–support interactions in supported metal catalysts.

DOI： 10.1021/acs.nanolett.1c03485

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PubMed

出版者・発行元：Chemical Engineering Journal  

The synthesis of phenol by one-pot oxidation of benzene with dioxygen (O2) is a significant conceptual and practical challenge because benzene has low reactivity to O2 at room temperature and ambient pressure. Furthermore, phenol is more reactive than benzene and is easily overoxidized, so complete oxidation is more likely to proceed in the benzene oxidation reaction, which generally results in lower phenol yield and selectivity. Herein, we report that a heteropolyacid H3PW12O40 functions as a photocatalyst for benzene oxidation reaction in an aqueous acetonitrile solution using O2 in high phenol yield (23–41%) and selectivity (80–90%). The addition of acetonitrile to the reaction solution significantly inhibited the complexation between phenol and H3PW12O40, preventing phenol overoxidation. Furthermore, no decomposition of H3PW12O40 during the reaction was evidenced by UV–VIS spectra. This photocatalyst can be used repeatedly with only a slight decrease in the rate of phenol formation. For the mechanistic study, the initial rates, which depended on the reaction conditions, were investigated in detail. The benzene oxidation under anaerobic conditions was also conducted as a control experiment. A color change of reaction solution from colorless to blue has confirmed the reduction of H3PW12O40 during the catalytic process and the formation of reduced H3PW12O40 detected in the UV–VIS spectra. A kinetic isotope effect (KIE), kH/kD = 1.15, is found for the oxidation of benzene/benzene‑d6, indicating electron transfer is the principal C−H bond activation process in the mechanism. We identified hydrogen peroxide as an intermediate and found that phenol was generated in both the photocatalytic reduction and reoxidation process in our system.

DOI： 10.1016/j.cej.2021.131369

Web of Science

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