Papers - Kondoh, Hiroshi

Acid-Base Bifunctional Catalysis of the Lewis Acidic Isolated Co(OH)<inf>2</inf> and Basic N Anion Generated from CeO<inf>2</inf> and 2-Cyanopyridine

Tamura M., Haga M., Junkaew A., Asada D., Ichikawa R., Toyoshima R., Nakayama A., Kondoh H., Nakagawa Y., Tomishige K.

ACS Catalysis 14 ( 17 ) 13015 - 13029 2024.09

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Acid-base bifunctional catalysts, which have both acid and base sites that are arranged at an appropriate distance, are one of the effective catalyst categories and have been extensively studied as a simple and effective method for designing heterogeneous and homogeneous catalysts in both the laboratories and industry. Recently, we found that a heterogeneous-homogeneous hybrid strong base site of N- was constructed only by mixing 2-cyanopyridine and CeO2 in the solution, where the N- site was formed by the covalent bonding between the lattice O atom of CeO2 and the C atom of the CN group in 2-cyanopyridine. Herein, an effective acid-base bifunctional catalyst with proximal sites of the heterogeneous-homogeneous hybrid base site and metal species-derived Lewis acid site is presented. The introduction of Co species into CeO2 forms isolated Co(OH)2 on CeO2, and further introduction of 2-cyanopyridine generates the heterogeneous-homogeneous hybrid base site of N- near the Co(OH)2 without the interference of these sites. The acid-base bifunctional sites work cooperatively to provide about 10-fold higher activity to the hydromethoxylation of acrylonitrile than the heterogeneous-homogeneous hybrid base site alone. Catalyst characterizations such as XRD, TEM, UV-vis, NO adsorption, XPS, Raman, XAS, NH3-TPD and in situ XPS, DFT calculations, and kinetic studies show that acrylonitrile and methanol are activated by the Lewis acidic Co(OH)2 and the hybrid base site, respectively, and the cooperative work results in the large rate enhancement.

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In Situ Observation of Charge Transfer in the Cocatalyst-Loaded SrTiO<inf>3</inf>:Al Photocatalyst under UV Irradiation by Conversion-Electron-Yield Soft-X-ray Absorption Spectroscopy

Wang Z., Toyoshima R., Yoshida M., Mase K., Kondoh H.

Journal of Physical Chemistry C 128 ( 22 ) 9193 - 9201 2024.06

ISSN  19327447

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We developed an in situ observation system for photoinduced surface phenomena under ambient-pressure conditions based on conversion-electron-yield soft-X-ray absorption spectroscopy (CEY-SXAS). We applied this technique to in situ observation for photoinduced hole transfer in a highly efficient photocatalyst, Al-doped SrTiO3 (STO:Al), with cocatalysts, Rh/Cr2O3 for the hydrogen evolution reaction (HER) site and the CoOOH oxygen evolution reaction (OER) site. In situ Co L-edge CEY-SXAS measurements under saturated water vapor conditions revealed that UV-vis irradiation readily induces oxidation of Co in the CoOOH OER site, which provides evidence for photoinduced hole transfer from the STO:Al site to the OER site. Interestingly, without loading of the Rh/Cr2O3 HER site or without introducing water vapor, no photoinduced hole transfer to the CoOOH OER site was observed. Coexisting of the Rh/Cr2O3 HER site and water vapor on the STO:Al surface is crucial to the hole transfer to the OER site under photoirradiation.

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Dehydrogenative oxidation of hydrosilanes using gold nanoparticle deposited on citric acid-modified fibrillated cellulose: unveiling the role of molecular oxygen

Suwattananuruk B., Uetake Y., Ichikawa R., Toyoshima R., Kondoh H., Sakurai H.

Nanoscale 16 ( 26 ) 12474 - 12481 2024.05

ISSN  20403364

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Efficient and environmentally friendly synthesis of silanols is a crucial issue across the broad fields of academic and industrial chemistry. Herein, we describe the dehydrogenative oxidation of hydrosilane using a gold nanoparticle catalyst supported by fibrillated citric acid-modified cellulose (F-CAC). Au:F-CAC catalysts with various particle sizes (1.7 nm, 4.9 nm, and 7.7 nm) were prepared using the trans-deposition method, a technique previously reported by our group. These catalysts exhibited significant catalytic activity to produce silanols with high turnover frequency (TOF) of up to 7028 h−1. Recycling experiments and transmission electron microscopy (TEM) observation represented the high durability of Au:F-CAC under the reaction conditions, allowing kinetic studies on size dependency. Mechanistic studies were conducted, including isotope labelling experiments, kinetics, and various spectroscopies. Notably, the near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) of the model catalyst (Au:PVP) revealed the formation of catalytically active cationic Au sites on the surface through the adsorption of molecular oxygen, providing a new insight into the reaction mechanism.

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Understanding of a Pt thin-film H<inf>2</inf> sensor under working conditions using AP-XPS and XAFS

Toyoshima R., Tanaka T., Kato T., Abe H., Uchida K., Kondoh H.

Chemistry Letters 53 ( 2 )  2024.02

ISSN  03667022

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The operating principle of a Pt thin-film H2 gas sensor was investigated using a combination of surface sensitive ambient-pressure X-ray photoelectron spectroscopy and bulk sensitive X-ray absorption fine structure techniques, which provided chemical and structure information under working conditions, coupled with electric resistivity measurements. It is shown that the sensor response was in a linear relation with both coverages of H and O atoms on the Pt surface. Moreover, the bulk structure of Pt remains unchanged under H2 exposure. These observations support that the resistivity change is associated with electron scattering in the near-surface region.

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Promotional Effect of Ag on the Catalytic Decomposition of N<inf>2</inf>O in the Presence of O<inf>2</inf> over the Al<inf>2</inf>O<inf>3</inf>-Supported Rh Catalyst

Jing Y., He C., Zhang N., Murano Y., Toyoshima R., Kondoh H., Kageyama Y., Inomata H., Toyao T., Shimizu K.I.

ACS Catalysis 13 ( 19 ) 12983 - 12993 2023.10

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Catalytic decomposition of N2O into N2 and O2 is one of the most important techniques for removing N2O from the atmosphere to curb global warming. Supported RhOx catalysts are known to show high efficiency for N2O decomposition, even in the presence of O2, compared with other materials, such as supported metal oxides and Fe-based zeolite catalysts. In this study, the addition of Ag was found to enhance the efficiency of an Al2O3-supported RhOx catalyst (RhOx/Al2O3) for N2O decomposition. The promotional effect of Ag was investigated using various operando spectroscopic methods, including X-ray absorption spectroscopy, diffuse reflectance UV-vis spectroscopy (DR UV-vis), ambient-pressure X-ray photoelectron spectroscopy, and kinetic studies. The results demonstrated that the addition of Ag enhanced the catalytic efficiency of the supported RhOx catalysts by enhancing the thermal reduction of Rh oxide, which was identified as the rate-determining step, especially at low temperatures.

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Bifunctionality of Re Supported on TiO<inf>2</inf> in Driving Methanol Formation in Low-Temperature CO<inf>2</inf> Hydrogenation

Phongprueksathat N., Ting K.W., Mine S., Jing Y., Toyoshima R., Kondoh H., Shimizu K.I., Toyao T., Urakawa A.

ACS Catalysis 13 ( 16 ) 10734 - 10750 2023.08

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Low temperature and high pressure are thermodynamically more favorable conditions to achieve high conversion and high methanol selectivity in CO2 hydrogenation. However, low-temperature activity is generally very poor due to the sluggish kinetics, and thus, designing highly selective catalysts active below 200 °C is a great challenge in CO2-to-methanol conversion. Recently, Re/TiO2 has been reported as a promising catalyst. We show that Re/TiO2 is indeed more active in continuous and high-pressure (56 and 331 bar) operations at 125-200 °C compared to an industrial Cu/ZnO/Al2O3 catalyst, which suffers from the formation of methyl formate and its decomposition to carbon monoxide. At lower temperatures, precise understanding and control over the active surface intermediates are crucial to boosting conversion kinetics. This work aims at elucidating the nature of active sites and active species by means of in situ/operando X-ray absorption spectroscopy, Raman spectroscopy, ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Transient operando DRIFTS studies uncover the activation of CO2 to form active formate intermediates leading to methanol formation and also active rhenium carbonyl intermediates leading to methane over cationic Re single atoms characterized by rhenium tricarbonyl complexes. The transient techniques enable us to differentiate the active species from the spectator one on TiO2 support, such as less reactive formate originating from spillover and methoxy from methanol adsorption. The AP-XPS supports the fact that metallic Re species act as H2 activators, leading to H-spillover and importantly to hydrogenation of the active formate intermediate present over cationic Re species. The origin of the unique reactivity of Re/TiO2 was suggested as the coexistence of cationic highly dispersed Re including single atoms, driving the formation of monodentate formate, and metallic Re clusters in the vicinity, activating the hydrogenation of the formate to methanol.

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Operando Spectroscopic Study of Reduction and Oxidation Half-Cycles in NH<inf>3</inf>-SCR over CeO<inf>2</inf>-Supported WO<inf>3</inf>

Kubota H., Jing Y., Wan L., Tong J., Zhang N., Mine S., Toyao T., Toyoshima R., Kondoh H., Ferri D., Shimizu K.I.

ACS Catalysis 13 ( 13 ) 9274 - 9288 2023.07

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Operando spectroscopies (in situ Ce and W L3-edge X-ray absorption near-edge structure, ultraviolet-visible (UV-vis), and infrared (IR) spectroscopies, combined with online analysis of gas-phase products) were exploited to elucidate reduction/oxidation half-cycles in the selective catalytic reduction of NO with NH3 (NH3-SCR) over WO3-loaded CeO2. The Ce4+ species was reduced by NO + NH3 to yield N2 and Ce3+ species (reduction half-cycle), which was then reoxidized by O2 (oxidation half-cycle). The oxidation state of the W6+ species remained unchanged under redox conditions. IR and theoretical results indicated that the reduction half-cycle started with the reaction of W6+-OH and adjacent Ce4+-O with NO to afford Ce3+ species and gaseous HONO, which was converted to NO+ species on the catalyst. The NO+ species then reacted with NH3 to generate N2

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Promoting effect of basic metal additives on DeNOx reactions over Pt-based three-way catalysts

Jing Y., Wang G., Mine S., Kawai J., Toyoshima R., Kondoh H., Zhang X., Nagaoka S., Shimizu K.i., Toyao T.

Journal of Catalysis (Journal of Catalysis)  416   209 - 221 2022.12

ISSN  00219517

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Pt has been economically favored over Rh and Pd. However, Pt-based three-way catalysts (TWCs) have been studied less than Pd- and Rh-based TWCs; therefore, their properties have not yet been sufficiently evaluated, especially under conditions relevant to modern three-way catalysis operation, wherein deviations from stoichiometric conditions are often encountered. In this study, we examined the promotional effect of basic metal additives in Pt/M/Al2O3 (M = Ba, La, Sr) on the efficiency of three-way catalytic reactions. The catalytic activities of the Pt/M/Al2O3 catalysts for NO, CO, and total hydrocarbons were superior to those of Pt/Al2O3; moreover, Ba enhanced the catalytic activity of Pt-based catalysts more efficiently than La and Sr. The best-performing catalyst, Pt/Ba/Al2O3, was subjected to kinetic studies and various in situ/operando spectroscopic experiments, namely, X-ray absorption spectroscopy, infrared spectroscopy, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), to investigate the role of Ba in the NO reduction reaction. The Pt0 species loaded on Ba/Al2O3 were more electron-rich than those loaded on Al2O3, thereby promoting NO dissociation into N and O atoms, as revealed by the AP-XPS results. Moreover, the efficient formation of intermediate surface NOx species, including nitrites and nitrates, and their reactivities toward reductant gases, such as H2 or CO, were critical for promoting the effect of Ba on the NO reduction reaction.

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Origin of the High Selectivity of the Pt-Rh Thin-Film H<inf>2</inf>Gas Sensor Studied by Operando Ambient-Pressure X-ray Photoelectron Spectroscopy at Working Conditions

Toyoshima R., Tanaka T., Kato T., Uchida K., Kondoh H.

Journal of Physical Chemistry Letters (Journal of Physical Chemistry Letters)  13 ( 36 ) 8546 - 8552 2022.09

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The Pt-Rh thin-film sensors exhibit excellent sensitivity and selectivity for H2 gas detection. Here, we studied the mechanism of highly selective detection of H2 by the Pt-Rh thin-film sensors with ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) measurements at working conditions, which were paralleled with electric resistivity measurements. The elemental composition and chemical state of surface Pt and Rh drastically change depending on the background gas environments, which directly link to the sensor response. It is revealed that surface segregated Pt atoms accelerate dissociative adsorption of H2, resulting in a reduction of the sensor surface and then a decrease of electric resistivity of the film, whereas a thin oxidized Rh layer blocks dissociation of the other reducing agent, that is, NH3. This is supported from the adsorption energetics obtained by the density functional theory (DFT) calculations.

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Substrate Effect of Ir and Rh on Surface ReO<inf>x</inf>Species under a Hydrogen Atmosphere Studied by NAP-XPS

Chen J., Kawai J., Ozawa K., Toyoshima R., Tomishige K., Kondoh H.

Journal of Physical Chemistry C (Journal of Physical Chemistry C)  126 ( 28 ) 11544 - 11552 2022.07

ISSN  19327447

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The substrate effect of M-Re (M is a noble metal) bifunctional catalysts for C-O hydrogenolysis has been studied by using single-crystal substrates including Ir(111) and Rh(111) with in situ near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). Compared with Ir-Re and Rh-Re nanoparticle systems reported in the literature, the single crystals Ir(111) and Rh(111) have shown a more significant substrate effect in determining the surface Re species under a H2 atmosphere at elevated temperatures. It has been found that the hydrogen dissociation and spillover efficiency as the intrinsic property of the noble metals significantly impacts the surface species. A surface that supplies hydrogen more efficiently results in a lower overall oxidation state of Re. Most importantly, the chemical environment of OH species is also closely related to the hydrogen spillover; that is, the more efficient hydrogen spillover, the lower is the oxidation state of Re(-OH). Because the Re-OH sites are commonly considered as the active sites for terminal binding of the reactant molecules, the noble-metal substrates are expected to impact the binding strength of the adsorbate species and hence the overall catalytic activity by tuning the acidity of the Re-OH sites.

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A newly designed compact CEY-XAFS cell in the soft X-ray region and its application to surface XAFS measurements under ambient-pressure conditions without photoinduced side effects

Shimizu H., Toyoshima R., Isegawa K., Mase K., Nakamura J., Kondoh H.

Physical Chemistry Chemical Physics (Physical Chemistry Chemical Physics)  24 ( 5 ) 2988 - 2996 2022.02

ISSN  14639076

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We report a newly designed compact cell to measure XAFS spectra with the conversion electron yield (CEY) method in the soft X-ray region under ambient-pressure gas conditions. Secondary electrons generated from the gas and sample by collision of X-ray-absorption-induced Auger electrons are collected by a positively biased collector electrode to obtain XAFS spectra. It was confirmed that this cell is applicable to soft X-ray surface XAFS measurements for different types of materials such as insulating organic materials and metal oxides under 1 bar gas conditions. During the measurements, photoinduced side effects were observed; i.e. photoinduced degradation of organic materials and photoinduced reduction/oxidation of metal oxides. We found that these photoinduced side effects can be sufficiently suppressed by controlling the measuring conditions. The presented measuring approach will enable surface XAFS spectra to be obtained in the soft X-ray region for various types of functional materials under ambient-pressure working conditions. This journal is

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Ligand effects on surface oxide at RhPd(100) alloy surfaces: A density functional theory calculation study

Shirahata N., Toyoshima R., Yoshida M., Ueda K., Mase K., Mun B.S., Kondoh H.

Surface Science (Surface Science)  716 2022.02

ISSN  00396028

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Density functional theory calculations were applied to a study on ligand effects on a Pd surface oxide formed on RhPd(100) alloy surfaces. It was found that chemical composition of the topmost layer of alloy significantly influences on the electronic structure of the Pd surface oxide. Such interlayer ligand effects are originating from the Rh−O and Pd−O interactions between the topmost layer of alloy and the Pd surface oxide. These effects give rise to substantial changes in binding energies of adsorbates and could change catalytic activity depending on atomic fraction of the Rh−Pd alloy.

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Materials Science Research by Ambient Pressure X-ray Photoelectron Spectroscopy Systems at Synchrotron Radiation Facilities in Japan: Applications in Energy, Catalysis, and Sensors

Yamamoto S., Takagi Y., Koitaya T., Toyoshima R., Horio M., Matsuda I., Kondoh H., Yokoyama T., Yoshinobu J.

Synchrotron Radiation News (Synchrotron Radiation News)  35 ( 3 ) 19 - 25 2022

ISSN  08940886

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Direct Chlorination of Ethene on ZnO (0001̅) by Hot Chlorine Atoms

Doh W.H., Kondoh H., Ahn E., Park D., Cho D., Kim C.M.

Journal of Physical Chemistry C (Journal of Physical Chemistry C)  127 ( 18 ) 8523 - 8528 2022

ISSN  19327447

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The interaction between ethene and Cl2 on ZnO(0001̅) has been investigated using X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. At 110 K, the Cl2 molecule is perpendicularly adsorbed on ZnO(0001̅). Upon heating, Cl2 is dissociated on the surface in the temperature range of 200-230 K. When the surface coadsorbed with Cl2 and ethene is heated, the desorption of 1,2-dichloroethane is observed at ∼230 K. The desorption temperature is comparable to the dissociation temperature of Cl2 on ZnO(0001̅). Ethene does not react with Cl atoms chemisorbed on ZnO(0001̅). We propose that “hot” Cl atoms, which are produced during thermal dissociation of Cl2, promote the direct chlorination of C2H4. The energy of the hot Cl atoms is calculated to be maximum 27.5 kcal/mole higher than the energy of the chemisorbed Cl atoms.

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Assessing nickel oxide electrocatalysts incorporating diamines and having improved oxygen evolution activity using operando UV/visible and X-ray absorption spectroscopy

Miura T., Tsunekawa S., Onishi S., Ina T., Wang K., Watanabe G., Hu C., Kondoh H., Kawai T., Yoshida M.

Physical Chemistry Chemical Physics (Physical Chemistry Chemical Physics)  23 ( 40 ) 23280 - 23287 2021.10

ISSN  14639076

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The electrolysis of water using renewable energy is a promising approach to developing a sustainable hydrogen-based economy. To improve the efficiency of this process, it will be necessary to develop highly active electrocatalysts that promote the oxygen evolution reaction (OER). In the present study, the OER activity of a nickel oxide electrocatalyst was dramatically improved following the addition of a diamine to the electrolyte solution during electrodeposition. Operando UV/vis absorption spectroscopy was used to assess a number of nickel catalysts containing various diamines and other organic compounds. The data indicate that Ni(ii) complexes were formed with the diamines during electrodeposition. Consequently, the catalytic activity of these materials was enhanced based on increased concentrations of active reaction sites for the OER process. Ni K-edge X-ray absorption spectra showed that these catalysts were composed of γ-NiOOH with a Ni3.6+ valence state. The coordination of the diamine molecules to the γ-NiOOH produced structural distortion that contributed to improved OER activity. This structural distortion is likely the most important factor in enhancing the OER activity of inorganic-organic composite catalysts.

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In situ AP-XPS study on reduction of oxidized Rh catalysts under CO exposure and catalytic reaction conditions

Toyoshima R., Ueda K., Koda Y., Kodama H., Sumida H., Mase K., Kondoh H.

Journal of Physics D: Applied Physics (Journal of Physics D: Applied Physics)  54 ( 20 )  2021.05

ISSN  00223727

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Reduction of oxidized Rh catalysts under carbon monoxide (CO) exposure and reaction conditions were studied by using ambient-pressure x-ray photoelectron spectroscopy. First, Rh powders pressed into a pellet were deeply oxidized and the reduction process under 100 mTorr CO environment was monitored in situ at different temperatures. The oxidized Rh surfaces are composed of Rh2O3 and RhO2, the latter of which is more segregated near the surface. Both oxide species are reduced simultaneously to the metallic state; kinetic analyses indicate that the activation energy of the reduction of the Rh oxides is 1.68 eV, which is a little larger than those for Pd oxides, probably due to a stronger Rh-O interaction. Reduction of oxidized Rh nano-particles deposited on SiO2 under two reaction conditions (CO + O2 and CO + NO + O2) was observed with increasing temperature. It was found that the reduction temperature shifts to the higher temperature in the presence of NO, even though the S-factors are almost the same. The NO molecule more strongly prevents the reduction of oxidized Rh catalyst compared to O2.

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Formation and behavior of carbonates on Ag(110) in the presence of ethylene and oxygen

Isegawa K., Ueda K., Amemiya K., Mase K., Kondoh H.

Journal of Physical Chemistry C (Journal of Physical Chemistry C)  125 ( 17 ) 9032 - 9037 2021.05

ISSN  19327447

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Intermediate species formed on Ag(110) surfaces under the presence of ethylene and oxygen in the sub-Torr pressure range were studied by near-ambient-pressure X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) measurements. Carbonates are clearly observed exclusively under an ethylene-rich condition (0.2 Torr ethylene and 0.04 Torr oxygen; ethylene/oxygen = 5) at a high temperature of 500 K or relatively low-temperature conditions (≤470 K) at an oxygen-rich gas ratio (ethylene/oxygen = 1/5). NEXAFS results support the formation of carbonates and indicate that the carbonates are adsorbed almost parallel to the Ag(110) surface. The carbonates coexist with surface oxides with different composition ratios depending on the ethylene/oxygen pressure ratio and surface temperature. From these results we propose that the carbonates are formed by reaction(s) between ethylene and oxygen on the Ag(110) surface.

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Detailed Characterization of MoO<inf>x</inf>-Modified Rh Metal Particles by Ambient-Pressure XPS and DFT Calculations

Toyoshima R., Kawai J., Isegawa K., Kondoh H., Junkaew A., Nakayama A., Asano T., Tamura M., Nakagawa Y., Yabushita M., Tomishige K.

Journal of Physical Chemistry C (Journal of Physical Chemistry C)  125 ( 8 ) 4540 - 4549 2021.03

ISSN  19327447

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Characterization of Mo species on Rh metal particles in Rh-MoOx/C catalyst for C-O hydrogenolysis reactions was carried out with in situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and density functional theory (DFT) calculations. The as-prepared Rh-MoOx/C sample with high oxidation states of Rh3+, Rh4+ and Mo6+ was reduced with 0.2 Torr of H2. All the Rh species and most Mo species were reduced to Rh0 and Mo4+ during the heating to 570 K. The thickness of the Mo layers after the reduction was calculated by a numerical analysis based on the XPS intensity ratio and a uniform adlayer stacking model. The calculated averaged thickness was about 0.3 nm, suggesting the formation of Mo species with a monolayer order on the metallic Rh particle surface. The O 1s XPS showed the presence of Mo-OH and Mo-O oxygen species with a ratio of 1.4 in reduced Rh-MoOx/C. Considering the presence of residual Mo6+ species with a large number of Mo6+-O bonds, the ratio of Mo4+-OH to Mo4+-O is estimated to be 2, suggesting the formation of MoO(OH)2. The DFT calculations of various monomeric MoOxHy species on the Rh(111) surface were carried out, and the stability was examined by the ab initio thermodynamic approach. The relative stability is changed when the surface coverage of hydrogen atoms is taken into account. The MoO(OH)2 species is calculated to be the most stable species in the presence of surface hydrogens over a wide range of conditions, including those for the catalytic reaction (ca. 400 K, 100-1 MPa H2).

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Initial oxidation of GaAs(100) under near-realistic environments revealed by: In situ AP-XPS

Toyoshima R., Murakami S., Eguchi S., Amemiya K., Mase K., Kondoh H.

Chemical Communications (Chemical Communications)  56 ( 94 ) 14905 - 14908 2020.12

ISSN  13597345

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In situ monitoring of initial oxidation of GaAs surfaces was performed under (near-) realistic oxidizing environments, using ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). The surface chemical states drastically change with time. The oxidation process at the sub-nano-meter-scale exhibits a significantly small activation energy, which can be regarded as a quasi-barrier-less oxidation. This journal is

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How Rh surface breaks CO<inf>2</inf> molecules under ambient pressure

Kim J., Ha H., Doh W.H., Ueda K., Mase K., Kondoh H., Mun B.S., Kim H.Y., Park J.Y.

Nature Communications (Nature Communications)  11 ( 1 )  2020.12

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Utilization of carbon dioxide (CO2) molecules leads to increased interest in the sustainable synthesis of methane (CH4) or methanol (CH3OH). The representative reaction intermediate consisting of a carbonyl or formate group determines yields of the fuel source during catalytic reactions. However, their selective initial surface reaction processes have been assumed without a fundamental understanding at the molecular level. Here, we report direct observations of spontaneous CO2 dissociation over the model rhodium (Rh) catalyst at 0.1 mbar CO2. The linear geometry of CO2 gas molecules turns into a chemically active bent-structure at the interface, which allows non-uniform charge transfers between chemisorbed CO2 and surface Rh atoms. By combining scanning tunneling microscopy, X-ray photoelectron spectroscopy at near-ambient pressure, and computational calculations, we reveal strong evidence for chemical bond cleavage of O‒CO* with ordered intermediates structure formation of (2 × 2)-CO on an atomically flat Rh(111) surface at room temperature.

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Operando Observations of a Manganese Oxide Electrocatalyst for Water Oxidation Using Hard/Tender/Soft X-ray Absorption Spectroscopy

Tsunekawa S., Yamamoto F., Wang K.H., Nagasaka M., Yuzawa H., Takakusagi S., Kondoh H., Asakura K., Kawai T., Yoshida M.

Journal of Physical Chemistry C (Journal of Physical Chemistry C)  124 ( 43 ) 23611 - 23618 2020.10

ISSN  19327447

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A layered manganese oxide catalyst containing K+ cations [K/MnOx catalyst] was developed, and its ability to efficiently decompose water was demonstrated. Operando hard/tender/soft X-ray absorption fine structure (XAFS) techniques were used to investigate the function of the K/MnOx catalyst under working conditions. The Mn valency depended on the potential and the amount of K+ cation adsorption. Mn K-edge (hard X-ray) XAFS measurements for the K/MnOx catalyst suggested that the Mn in the catalyst was an Mn3+ species with an octahedral δ-MnO2 structure at a lower electrode potential, which changed reversibly to an Mn4+ species with a δ-MnO2 structure at higher potential during oxygen evolution. A similar result was obtained from operando O K-edge (soft X-ray) XAFS. The chemical state of K species was analyzed using operando K K-edge (tender X-ray) XAFS, which indicated that K+ cations were intercalated with hydrated states in the δ-MnO2 layers. These operando XAFS results demonstrated that the layered δ-MnO2 containing hydrated K+ cations functioned as efficient oxygen evolution electrocatalysts because of the presence of Mn3+ reaction sites.

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In situ AP-XPS analysis of a Pt thin-film sensor for highly sensitive H<inf>2</inf>detection

Toyoshima R., Tanaka T., Kato T., Uchida K., Kondoh H.

Chemical Communications (Chemical Communications)  56 ( 70 ) 10147 - 10150 2020.09

ISSN  13597345

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In situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) combined with resistivity measurement was performed for a Pt thin-film H2 gas sensor. We experimentally demonstrate that the chemical state of the Pt surface changes under working conditions, and it directly links to the sensing performance. Moreover, the operating principle is discussed at the atomic scale. This journal is

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Promotional Effect of la in the Three-Way Catalysis of La-Loaded Al<inf>2</inf>O<inf>3</inf>-Supported Pd Catalysts (Pd/La/Al<inf>2</inf>O<inf>3</inf>)

Jing Y., Cai Z., Liu C., Toyao T., Maeno Z., Asakura H., Hiwasa S., Nagaoka S., Kondoh H., Shimizu K.I.

ACS Catalysis (ACS Catalysis)  10 ( 2 ) 1010 - 1023 2020.01

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La-loaded Al2O3 (La/Al2O3) is a practical support for three-way catalysis (TWC) reactions. Although it has been reported that the addition of La to Al2O3 results in improved thermal stability to retain high specific surface areas, its effect on the catalytic reduction of NOx (DeNOx) has not been studied systematically. Herein, we describe the role of La in La/Al2O3-supported Pd catalysts (Pd/La/Al2O3) for TWC reactions. For that purpose, we employed various in situ spectroscopic studies, including infrared (IR), X-ray absorption fine structure (XAFS), and near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) in combination with density functional theory (DFT) calculations. The obtained results revealed that Pd0 species supported on La/Al2O3 are more electron-deficient compared to those on pristine Al2O3 without La(Pd/Al2O3). Kinetic studies using powdered catalysts revealed that the addition of La suppresses the poisoning effect by CO during the DeNOx reactions. In addition to the catalytic tests with powdered catalysts, monolithic honeycomb forms of the catalysts were prepared and employed for TWC reactions, which showed that Pd/La/Al2O3 exhibits higher DeNOx activity than Pd/Al2O3. In this study, we also reexamined the effective loading amount of La, which has traditionally been ∼3-5 wt % of La for TWC processes in order to retain the high specific surface area of the La/Al2O3 supports. Our investigations showed that an increased La loading (15 wt %) is even more effective for the DeNOx reactions tested in this study due to the higher reactivity toward NO and the greater suppression of the poisoning effect of CO. The developed catalyst Pd/La(15)/Al2O3 has also been tested in a commercial vehicle and has been evaluated on a practical driving mode test cycle (LA-4; city cycle of U.S. Federal and California), where it showed a better catalytic performance than the conventionally used Pd/La(3-5)/Al2O3 catalysts. Our study suggests that the loading amount of La in Pd/La/Al2O3 catalysts needs to be adjusted depending on the application systems, considering not only the support stability (surface areas) but also the promotional effect in the TWC process.

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Operando observations of reactive metal–Oxide structure formation on the Pt<inf>3</inf>Ni(111) surface at near-ambient pressure

Kim J., Doh W.H., Kondoh H., Mase K., Gallet J.J., Bournel F., Mun B.S., Park J.Y.

Journal of Electron Spectroscopy and Related Phenomena (Journal of Electron Spectroscopy and Related Phenomena)  238 2020.01

ISSN  03682048

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The formation of interfacial metal–oxide structures on the Pt3Ni(111) bimetallic surface was investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) techniques at near-ambient pressure (NAP). Direct observation of surface images clearly shows the occurrence of surface segregation of the sub-surface Ni depending on the surrounding gas-phase conditions. Especially, the prepared topmost Pt-skin layer of the Pt3Ni(111) is altered by Ni oxide segregation that makes an interfacial Pt-NiO1−x nanostructure with dissociated oxygen. This metal–oxide interface could provide active sites for more-efficient carbon monoxide (CO) conversion processes under mixed CO/O2 gas environments; the associated specific chemical binding energy was identified using NAP-XPS. The combined operando observations from the NAP-STM and NAP-XPS on the Pt3Ni(111) surface reveal that the interfacial metal–oxide structure is strongly correlated with the origin of the enhanced catalytic activity at thermodynamic equilibrium.

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Improvement in cobalt phosphate electrocatalyst activity toward oxygen evolution from water by glycine molecule addition and functional details

Yamada K., Hiue T., Ina T., Wang K., Kondoh H., Sakata Y., Lee Y.L., Kawai T., Yoshida M.

Analytical Sciences (Analytical Sciences)  36 ( 1 ) 35 - 40 2020

ISSN  09106340

　View Summary

Electrochemical water splitting using renewable energy shows promise for the development of sustainable hydrogen production methods. The process requires a highly active electrocatalyst for oxygen evolution to improve the overall water splitting efficiency. The present study showed that oxygen evolution improved dramatically upon the addition of glycine to cobalt phosphate, when the glycine was added to the electrolyte solution during electrodeposition. The functionality of the organic molecules was investigated using in situ UV-vis absorption, in situ X-ray absorption fine structure, and in situ infrared (IR) absorption spectroscopy in the attenuated total reflection mode. The results demonstrated that the glycine molecules assembled cobalt oxide clusters composed of CoO6 (CoOOH) octahedrons a few nanometers in diameter upon the electrodeposition of cobalt catalysts. This suggests that the cobalt-glycine catalyst can decompose water to oxygen gas efficiently, because the number of cobalt oxide clusters increased as active reaction sites upon the addition of glycine molecules.

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Orientation-Dependent Hindrance to the Oxidation of Pd-Au Alloy Surfaces

Toyoshima R., Amemiya K., Mase K., Kondoh H.

Journal of Physical Chemistry Letters (Journal of Physical Chemistry Letters)     9249 - 9254 2020

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Oxidation of monometallic Pd and bimetallic Pd3Au alloy surfaces are observed by in situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) at an elevated pressure (100 mTorr O2 ambient). It is directly evidenced that the alloying with Au hinders the surface oxidation of Pd3Au surfaces compared with monometallic Pd surfaces. Remarkably, the oxidation behavior is clearly different between Pd3Au(111) and (100) surfaces. The (100) surface has a relatively Pd-rich surface composition, and the surface oxide layer is formed, whereas the (111) surface has a Au-rich composition, and the surface oxidation is quite limited. A combined approach of experimental and theoretical techniques reveals that Pd/Au surface composition and atomic arrangement are key factors determining the oxidation behavior.

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Adsorption state of NO on Ir(111) surfaces under excess O <inf>2</inf> coexisting condition

Ikeda H., Koike Y., Shiratori K., Ueda K., Shirahata N., Isegawa K., Toyoshima R., Masuda S., Mase K., Nito T., Kondoh H.

Surface Science (Surface Science)  685   1 - 6 2019.07

ISSN  00396028

　View Summary

Iridium (Ir) exhibits a good efficiency for reduction of NO under excess O 2 coexisting conditions at temperatures higher than 250 °C. On the other hand, the advantage is lost at lower temperatures below 250 °C under O 2 existence, compared to any other platinum group metals. In this study, adsorption behavior of NO on Ir(111) single-crystal surfaces under excess O 2 coexisting conditions at the temperatures from room temperature to 250 °C has been studied by in-situ X-ray Photoelectron Spectroscopy (XPS). It is revealed that the coexisting O 2 induces formation of a high-density chemisorbed atomic oxygen (O) phase and the atomic O phase suppresses adsorption of NO at on-top sites significantly, which suggests that the suppression of NO adsorption causes a decrease in the ability of NO reduction at the lower temperatures.

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Influence of Surface Orientation on Electrochemical Properties of Boron-Doped Diamond

Ivandini T.A., Watanabe T., Matsui T., Ootani Y., Iizuka S., Toyoshima R., Kodama H., Kondoh H., Tateyama Y., Einaga Y.

Journal of Physical Chemistry C (Journal of Physical Chemistry C)  123 ( 9 ) 5336 - 5344 2019.03

ISSN  19327447

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To study the influence of crystal orientation on the electrochemical properties of boron-doped diamond (BDD), electrodes comprising (100) and (111) homoepitaxial single-crystal layers of BDD were investigated and these were compared with a thin polycrystalline BDD electrode. The BDD samples with similar amounts of boron of around 1020 cm-3 and resistivity of around 6 × 10-3 ? cm were prepared. Evaluation of the electrochemical reactivity of each of the samples with both H- and O-terminated surfaces showed that polycrystalline BDD was the most reactive, whereas the (111) samples proved to be more reactive than the (100) ones for single-crystal BDD. Moreover, considering the results of first-principles molecular dynamics simulations, it is proposed that surface transfer doping is the dominating factor for H-terminated surfaces, whereas the degree of band bending and the thickness of the space-charge layer are the dominating factors for O-terminated surfaces.

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Operando study of Pd(100) surface during CO oxidation using ambient pressure x-ray photoemission spectroscopy

Yu Y., Kim D., Lim H., Kim G., Koh Y.E., Kim D., Ueda K., Hiwasa S., Mase K., Bournel F., Gallet J.J., Rochet F., Crumlin E.J., Ross P.N., Kondoh H., Noh D.Y., Mun B.S.

AIP Advances (AIP Advances)  9 ( 1 )  2019.01

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The surface chemical states of Pd(100) during CO oxidation were investigated using ambient pressure x-ray photoelectron spectroscopy and mass spectroscopy. Under the reactant ratio of CO/O 2 = 0.1, i.e. an oxygen-rich reaction condition, the formation of surface oxides was observed with the onset of CO oxidation reaction at T = 525 K. As the reactant ratio (CO/O 2 ) increased from 0.1 to 1.0, ∼ 90 % surface oxides remains on surface during the reaction. Upon the formation of surface oxides, the core level shift of oxygen gas phase peak was observed, indicating that change of surface work function. As CO oxidation takes places, i.e. making a transition from CO covered surface to the oxidic surface, the work functions of surface oxide on Pd(100) and Pt(110) display opposite behavior.

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Formation of carbonate on Ag(111) under exposure to ethylene and oxygen gases evidenced by near ambient pressure XPS and NEXAFS

Isegawa K., Ueda K., Hiwasa S., Amemiya K., Mase K., Kondoh H.

Chemistry Letters (Chemistry Letters)  48 ( 2 ) 159 - 162 2019

ISSN  03667022

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The active oxygen species for ethylene epoxidation on Ag surfaces has been a long-standing issue. We conducted in situ observations of Ag(111) surfaces under exposure to ethylene and oxygen gases with near ambient pressure (NAP) X-ray photo-electron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. Combined results of these spectroscopies evidence that a carbonate species with a flat-lying configuration is formed on the Ag(111) surface at 370500 K under exposure to the NAP gas mixture of ethylene and oxygen.

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Operando NAP-XPS Observation and Kinetics Analysis of NO Reduction over Rh(111) Surface: Characterization of Active Surface and Reactive Species

Ueda K., Isegawa K., Amemiya K., Mase K., Kondoh H.

ACS Catalysis (ACS Catalysis)  8 ( 12 ) 11663 - 11670 2018.12

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NO reduction by CO on Rh(111) was investigated by near-ambient pressure X-ray photoelectron spectroscopy, mass spectrometry, and kinetic analysis. Under exposure to NO + CO mixed gases and with heating the surface from room temperature to 450 °C, NO dissociation and NO reduction reaction start simultaneously independent of gas pressure ratio of NO/CO, which indicates that NO dissociation triggers this reaction. From kinetic analyses based on observed adsorbate coverages under reaction conditions, the following two points are suggested: (i) NOhollow is a reactive species for N2 and N2O formation via N + NO reaction. (ii) At low temperatures, the N + NO reaction is dominant for N2 production, whereas above around 400 °C, the N + N reaction becomes dominant, which leads to an increase in N2 selectivity at the higher temperatures. Compared with the NO + CO reaction on Ir(111) surfaces, which exhibits a high N2 selectivity, the adsorption site of reactive NO and the availability of vacant surface sites could be key factors for the lower N2 selectivity for Rh(111).

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Adsorbate-driven reactive interfacial Pt-NiO<inf>1−</inf>x nanostructure formation on the Pt<inf>3</inf>Ni(111) alloy surface

Kim J., Park W.H., Doh W.H., Lee S.W., Noh M.C., Gallet J.J., Bournel F., Kondoh H., Mase K., Jung Y., Mun B.S., Park J.Y.

Science Advances (Science Advances)  4 ( 7 )  2018.07

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The origin of the synergistic catalytic effect between metal catalysts and reducible oxides has been debated for decades. Clarification of this effect, namely, the strong metal-support interaction (SMSI), requires an understanding of the geometric and electronic structures of metal-metal oxide interfaces under operando conditions. We show that the inherent lattice mismatch of bimetallic materials selectively creates surface segregation of subsurface metal atoms. Interfacial metal-metal oxide nanostructures are then formed under chemical reaction environments at ambient pressure, which thus increases the catalytic activity for the CO oxidation reaction. Our in situ surface characterizations using ambient-pressure scanning tunneling microscopy and ambient-pressure x-ray photoelectron spectroscopy exhibit (i) a Pt-skin layer on the Pt-Ni alloyed surface under ultrahigh vacuum, (ii) selective Ni segregation followed by the formation of NiO1−x clusters under oxygen gas, and (iii) the coexistence of NiO1−x clusters on the Pt-skin during the CO oxidation reaction. The formation of interfacial Pt-NiO1−x nanostructures is responsible for a highly efficient step in the CO oxidation reaction. Density functional theory calculations of the Pt3Ni(111) surface demonstrate that a CO molecule adsorbed on an exposed Pt atom with an interfacial oxygen from a segregated NiO1−x cluster has a low surface energy barrier of 0.37 eV, compared with 0.86 eV for the Pt(111) surface.

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Chemical state changes of Nafion in model polymer electrolyte fuel cell under oxygen/hydrogen gas atmosphere observed by S-K XANES spectroscopy

Isegawa K., Kim D., Kondoh H.

RSC Advances (RSC Advances)  8 ( 67 ) 38204 - 38209 2018

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Changes in the chemical states of the sulfonic groups of Nafion in a model polymer electrolyte fuel cell under an oxygen/hydrogen gas atmosphere were studied using sulfur K-edge XANES spectroscopy. First, the chemical state changes in the sulfonic acid groups of both cathode and anode electrodes due to humidity under oxygen/hydrogen gas flow were observed. Reversible spectral changes ascribed to the hydration and dehydration of the sulfonic acid group were observed at both electrodes. This result is similar to the experimental results obtained without introducing oxygen (helium/hydrogen). On the anode, some of the sulfonic acid groups were decomposed to atomic sulfur adsorbed on platinum (Sad) and the amount increased with time. On the cathode, the formation of Sad was suppressed under the oxygen atmosphere. Next, the effects of oxygen gas introduction onto Sad were examined. Sad was at once formed on both electrodes under dry conditions without an oxygen supply. By supplying oxygen gas, Sad on the cathode disappears. Therefore, the catalyst of the cathode has the ability to recover against the poisoning Sad, while that on the anode accumulates.

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Element selective oxidation on Rh-Pd bimetallic alloy surfaces

Kondoh H., Toyoshima R., Shirahata N., Hoda A., Yoshida M., Amemiya K., Mase K., Mun B.

Physical Chemistry Chemical Physics (Physical Chemistry Chemical Physics)  20 ( 45 ) 28419 - 28424 2018

ISSN  14639076

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The interactions between oxygen and Rh-Pd bimetallic alloy surfaces were investigated using surface sensitive experimental techniques and density functional theory calculations. The alloy surfaces were oxidized under 10-5 Torr and 100 mTorr oxygen upon heating above 250 °C. A thin Rh oxide layer was preferentially formed on a Rh1Pd9(100) surface, while a thin Pd oxide layer was formed on a Rh1Pd9(111) surface, though the Rh oxide is thermodynamically more stable irrespective of the surface orientation. Chemical analyses revealed that the initial Rh fraction for the (111) surface was significantly lower than that for the (100) surface, which suggests that the oxidized element on the surface is kinetically selected depending on the near surface initial composition.

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Dehydration Pathway for the Dissociation of Gas-Phase Formic Acid on Pt(111) Surface Observed via Ambient-Pressure XPS

KONDOH Hiroshi

J. Phys. Chem. C (The American Chemical Society)  122 ( 4 ) 2064 - 2069 2017.12

Joint Work, Accepted,  ISSN  19327447

　View Summary

While model studies of surface science under ultrahigh vacuum (UHV) have made significant contributions to understanding electrochemistry, many issues related to electrochemical phenomena still remain unanswered due to the extreme environmental differences between UHV and liquid conditions. Electrochemical formic acid (HCOOH) oxidation is one such example. While the dehydration step in the indirect oxidation pathway (HCOOH → H2O + COad → 2H+ + 2e- + CO2) is observed in the electrochemical oxidation of formic acid on Pt(111) surface, the surface science studies conducted in UHV condition reported the complete HCOOH dissociation to H2 and CO2 on Pt(111) surface with no adsorbed CO at room temperature. A dehydration mechanism may also exist in gas-phase HCOOH dissociation in some conditions different from UHV, but it has not been demonstrated with a surface science method due to pressure limitations. Using ambient pressure X-ray photoelectron spectroscopy (AP-XPS), we observed the dehydration mechanism of gas-phase HCOOH in unprecedented high pressure environment for the first time. This study is a demonstration of reconciling the disagreement between electrocatalysis and surface science by bridging the environment gap.

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Catalytic CO oxidation over Pd70Au30(111) alloy surface: spectroscopic evidence for Pd ensemble dependent activity

KONDOH Hiroshi

Chem. Commun. (The Royal Society of Chemistry)  53   12657 - 12660 2017.11

Joint Work, Accepted

Chemical states of surface oxygen during CO oxidation on Pt(110) surface revealed by ambient pressure XPS

KONDOH Hiroshi

J. Phys.: Condens. Matter. (IOP)  29   464001-(1) - 464001-(6) 2017.10

Research paper (scientific journal), Joint Work, Accepted

Ambient pressure phase transitions over Ir(111): At the onset of CO oxidation

KONDOH Hiroshi

J. Phys.: Condens. Matter. (IOP)  29   444002-(1) - 444002-(10) 2017.10

Research paper (scientific journal), Joint Work, Accepted

Operando Observation of NO Reduction by CO on Ir(111) Surface Using NAP-XPS and Mass Spectrometry: Dominant Reaction Pathway to N2 Formation under Near Realistic Conditions

K. Ueda, M. Yoshida, K. Isegawa, N. Shirahata, K. Amemiya, K. Mase, B. S. Mun and H. Kondoh

J. Phys. Chem. C (American Chemical Society)  121 ( 3 ) 1763 - 1769 2017.01

Accepted

Integration of Active Nickel Oxide Clusters by Amino Acids for Water Oxidation

M. Yoshida, S. Onishi, Y. Mitsutomi, F. Yamamoto, M. Nagasaka, H. Yuzawa, N. Kosugi and H. Kondoh

J. Phys. Chem. C (American Chemical Society)  121 ( 1 ) 255 - 260 2016.12

Accepted

In Situ Observations of Oxygen Evolution Cocatalysts on Photoelectrodes by X-ray Absorption Spectroscopy: Comparison between Cobalt-Phosphate and Cobalt-Borate

H. Kurosu, M. Yoshida, Y. Mitsutomi, S. Onishi, H. Abe and H. Kondoh

Electrochemistry (The Electrochemical Society of Japan)  84   779 - 783 2016.10

Accepted

In-situ S-K XANES study on polymer electrolyte fuel cell: Changes in chemical state of sulfonic group depending on humidity

K. Isegawa, T. Nagami, S. Jomori, M. Yoshida and H. Kondoh

Phys. Chem. Chem. Phys. (Royal Society of Chemistry)  18 ( 36 ) 25183 - 25190 2016.08

Accepted

Observation of surface reduction of NiO to Ni by surface-sensitive total reflection X-ray spectroscopy using Kramers-Kronig relations

H. Abe, T. Nakayama, Y. Niwa, H. Nitani, H. Kondoh and M. Nomura

Jpn. J. Appl. Phys. (The Japan Society of Applied Physics)  55   062401 2016.05

Joint Work, Accepted

Adsorption and Reaction of CO and NO on Ir(111) under Near Ambient Pressure Conditions

K. Ueda, K. Suzuki, R. Toyoshima, Y. Monya, M. Yoshida, K. Isegawa, K. Amemiya, K. Mase, B.S. Mun, M. A. Arman, E. Grånäs, J. Knudsen, J. Schnadt, H. Kondoh

Topics in Catalysis (Springer)  59 ( 5 ) 487 - 496 2016.03

Joint Work, Accepted

In-situ surface analysis of AuPd(110) under elevated pressure of CO

M.A. Languille, E. Ehret, H. C. Lee, C. K. Jeong , Ryo Toyoshima, H. Kondoh, K. Mase, Y. Jugnet, J.C. Bertolini, F.J. Cadete Santos Aires, B.S. Mun

Catalysis Today (Elsevier)  260   39 - 45 2016.02

Joint Work, Accepted

In situ analysis of catalytically active Pd surfaces for CO oxidation with near ambient pressure XPS

Kondoh, Hiroshi, Toyoshima, Ryo, Monya, Yuji, Yoshida, Masaaki, Mase, Kazuhiko, Amemiya, Kenta, Mun, Bongjin Simon

Catalysis Today 260   14 - 20 2016.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0920-5861

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Surface segregation and oxidation of Pt3Ni(111) alloys under oxygen environment

H. C. Lee, B. M. Kim, C. K. Jeong, R. Toyoshima, H. Kondoh, T. Shimada, B. Mao, Z. Liu, H. G. Lee, C.-Q. Huang, W. X. Li, P.N Ross, B. S. Mun

Catalysis Today (Elsevier)  260   3 - 7 2016.02

Joint Work, Accepted

CO Adsorption on Pd-Au Alloy Surface: Reversible Adsorption Site Switching Induced by High-Pressure CO

Toyoshima, Ryo, Hiramatsu, Nana, Yoshida, Masaaki, Amemiya, Kenta, Mase, Kazuhiko, Mun, Bongjin Simon, Kondoh, Hiroshi

J. Phys. Chem.　C 120 ( 1 ) 416 - 421 2016.01

Research paper (scientific journal),  ISSN  1932-7447

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Structural Relationship between CoO6 Cluster and Phosphate Species in a Cobalt-Phosphate Water Oxidation Catalyst Investigated by Co and P K-edge XAFS

Yoshida, Masaaki, Mineo, Takehiro, Mitsutomi, Yosuke, Yamamoto, Futaba, Kurosu, Hirokatsu, Takakusagi, Satoru, Asakura, Kiyotaka, Kondoh, Hiroshi

Chem. Lett. 45 ( 3 ) 277 - 279 2015.12

Research paper (scientific journal), Accepted,  ISSN  0366-7022

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Direct Observation of Active Nickel Oxide Cluster in Nickel-Borate Electrocatalyst for Water Oxidation by In Situ O K-edge X-ray Absorption Spectroscopy

M. Yoshida, Y. Mitsutomi, T. Mineo, M. Nagasaka, H. Yuzawa, N. Kosugi, H. Kondoh

J. Phys. Chem. C (American Chemical Society)  119 ( 33 ) 19279 - 19286 2015.07

Joint Work, Accepted

High-Pressure NO Induced Mixed Phase on Rh(111): Chemically-Driven Replacement

KONDOH Hiroshi

J. Phys. Chem. C (The American Chemical Society)  119 ( 6 ) 3033 - 3039 2015.01

Research paper (scientific journal), Joint Work, Accepted

High-pressure-induced dense CO overlayer on Pt(111) surface: A chemical analysis with in-situ near ambient pressure XPS

KONDOH Hiroshi

Phys. Chem. Chem. Phys. (The Royal Chemical Society)  16 ( 43 ) 23564 - 23567 2014.11

Research paper (scientific journal), Joint Work, Accepted

Photoexcited Hole Transfer to a MnOx Cocatalyst on a SrTiO3 Photoelectrode During Oxygen Evolution Studied by in situ X-ray Absorption Spectroscopy

KONDOH Hiroshi

J. Phys. Chem. C (The American Chemical Society)  118 ( 42 ) 24302 - 24309 2014.10

Research paper (scientific journal), Joint Work, Accepted

In situ XAFS Study of the Photo-induced Potential Shift of a MnOx Cocatalyst on a SrTiO3Photocatalyst

KONDOH Hiroshi

Chem. Lett. (The Chemical Society of Japan)  43 ( 11 ) 1725 - 1727 2014.09

Research paper (scientific journal), Joint Work, Accepted

Electrochromic Characteristics of a Nickel Borate Thin Film Investigated by In Situ XAFS and UV/vis Spectroscopy

KONDOH Hiroshi

Electrochemistry (The Electrochemical Society of Japan)  82 ( 5 ) 355 - 358 2014.05

Research paper (scientific journal), Accepted

Structure and Photo-Induced Charge Transfer of Pyridine Molecules Adsorbed on TiO2(110): A NEXAFS and Core-Hole-Clock Study

KONDOH Hiroshi

Electrochemistry (The Electrochemical Society of Japan)  82 ( 5 ) 341 - 345 2014.05

Research paper (scientific journal), Accepted

A Near-Ambient-Pressure XPS Study on Catalytic CO Oxidation Reaction over a Ru(101-0) Surface

KONDOH Hiroshi

Surf. Sci. (Elsevier)  621   128 - 132 2014.03

Research paper (scientific journal), Accepted

In-Situ Photoemission Observation of Catalytic CO Oxidation Reaction on Pd(110) under Near-Ambient-Pressure Conditions: Evidence for the Langmuir-Hinshelwood Mechanism

KONDOH Hiroshi

J. Phys. Chem. C (American Chemical Society)  117   20617 - 20624 2013.09

Research paper (scientific journal), Joint Work, Accepted

In situ observation of carrier transfer in the Mn-oxide/Nb:SrTiO3 photoelectrode by X-ray absorption spectroscopy

KONDOH Hiroshi

Chem. Commun. 49   7848 - 7851 2013.07

Research paper (scientific journal), Joint Work, Accepted

Photoelectron spectroscopic study of CO and NO adsorption on Pd(100) surface under ambient pressure conditions

KONDOH Hiroshi

Surf. Sci. 615   33 - 40 2013.04

Research paper (scientific journal), Joint Work, Accepted

Active Surface Oxygen for Catalytic CO Oxidation on Pd(100) Proceeding under Near Ambient Pressure Conditions

R. Toyoshima, M. Yoshida, Y. Monya, K. Suzuki, B. S. Mun, K. Amemiya, K. Mase, and KONDOH Hiroshi

J. Phys. Chem. Lett. 3   3182–3187 2012.10

Research paper (scientific journal), Joint Work, Accepted

Molecular orientation change during adsorption of NO and N2O on Ir(111) observed by real-time wavelength-dispersive x-ray absorption spectroscopy with polarization switching

K. Amemiya, M. Sakamaki, S. Nakamoto, M. Yoshida, K. Suzuki, KONDOH Hiroshi, T. Koide, K. Ito, K. Tsuchiya, K. Harada, H. Sasaki, T. Aoto, T. Shioya, T. Obina, S. Yamamoto, and Y. Kobayashi

Appl. Phys. Lett. 101   161601 2012.10

Research paper (scientific journal), Joint Work, Accepted

In-situ Ambient Pressure XPS Study of CO Oxidation Reaction on Pd(111) Surfaces

R. Toyoshima, M. Yoshida, Y. Monya, Y. Kousa, K. Suzuki, H. Abe, B. S. Mun, K. Mase, K. Amemiya, and KONDOH Hiroshi

J. Phys. Chem. C 116 ( 35 ) 18691–18697 2012.08

Research paper (scientific journal), Joint Work, Accepted

evelopment of soft X-ray time-resolved photoemission spectroscopy system with a two-dimensional angle-resolved time-of-flight analyzer at SPring-8 BL07LSU

M. Ogawa, S. Yamamoto, Y. Kousa, F. Nakamura, R. Yukawa, A. Fukushima, A. Harasawa, H. Kondoh, Y. Tanaka, A. Kakizaki, and I. Matsuda

Rev. Sci. Instrum. 83 ( 2 ) 023109 2012.02

Research paper (scientific journal), Joint Work

Topological transition in Bi1-xSbx studied as a function of Sb doping

F. Nakamura, Y. Kousa, A. A. Taskin, Y. Takeichi, A. Nishide, A. Kakizaki, M. D’Angelo, P. Lefevre, F. Bertran, A. Taleb-Ibrahimi, F. Komori, S. Kimura, H. Kondoh, Y. Ando, and I. Matsuda

Phys. Rev. B 84 ( 23 ) 235308 2011.12

Research paper (scientific journal), Joint Work

Real-time observation of CO oxidation reaction on Ir(111) surface at 33 ms resolution by means of wavelength-dispersive near-edge x-ray absorption fine structure spectroscopy

Kenta Amemiya, Yuka Kousa, Shuichi Nakamoto, Taiga Harada, Shogo Kozai, Masaaki Yoshida, Hitoshi Abe, Ryohei Sumii, Masako Sakamaki, KONDOH Hiroshi

Appl. Phys. Lett. 99 ( 7 ) 074104 2011.08

Research paper (scientific journal), Joint Work, Accepted

Ambient Pressure XPSによる準大気圧下の表面観測

KONDOH Hiroshi

触媒 53 ( 3 ) 183-189 2011.04

Research paper (scientific journal), Single Work

解き明かされる触媒表面の姿 －大気圧下測定で見えてくる反応条件下の触媒表面

KONDOH Hiroshi

化学 65 ( 7 ) 74-75 2010.07

Research paper (scientific journal), Single Work

Irreversible Change in the NO Adsorption State On Pt(111) Under High-Pressure Studied By AP-XPS, NEXAFS and STM

SHIMADA Toru Shimada, MUN Bongjin, NAKAI Ikuyo, BANNO Atsushi, ABE Hitoshi, OHTA Toshiaki, IWASAWA Yasuhiro, KONDOH Hiroshi

J. Phys. Chem. C. 114 ( 40 ) 17030-17035 2010.06

Research paper (scientific journal), Joint Work, Accepted

In-situ XPS/NEXAFSで見る表面反応

KONDOH Hiroshi

PETROTECH 33 ( 4 ) 289-293 2010.04

Research paper (scientific journal), Single Work

Mechanism of Ammonia Formation on Rh(111) Studied by Dispersive Near-Edge X-ray Absorption Fine Structure Spectroscopy

KONDOH Hiroshi

J. Phys. Chem. C 114 ( 5 ) 2164-2170 2010.01

Research paper (scientific journal), Joint Work, Accepted

Pretreatment Dependence of Adsorption Properties of Merocyanine Dye at Rutile (110) and (100) TiO2 Surfaces studied by C K-edge NEXAFS

KONDOH Hiroshi

J. Phys. Chem. C 113 ( 39 ) 17254–17261 2009.09

Research paper (scientific journal), Joint Work, Accepted

Adsorption and reaction of NO on the clean and nitrogen modified Rh(111) surfaces

KONDOH Hiroshi

J. Chem. Phys. 131 ( 8 ) 084704 2009.08

Research paper (scientific journal), Joint Work, Accepted

STM Study of Surface Species Formed by Methanol Adsorption on Stoichiometric and Reduced ZnO(101-0) Surfaces

KONDOH Hiroshi

J. Phys. Chem. C 113 ( 32 ) 14356–14362 2009.07

Research paper (scientific journal), Joint Work, Accepted

Mechanism of N+NO reaction on Rh(111) surfaces: a precursor-mediated reaction

KONDOH Hiroshi

J. Phys. Chem. C 113 ( 30 ) 13257-13265 2009.07

Research paper (scientific journal), Joint Work, Accepted

Proton transfer in water-hydroxyl mixed overlayers on Pt(111): Combined approach of laser desorption and spatially-resolved x-ray photoelectron spectroscopy

KONDOH Hiroshi

Surface Science 603 ( 10-12 ) 1690-1695 2009.06

Research paper (scientific journal), Single Work

PbS Cubes with Pyramidal Pits: An Exampple of Etching Growth

KONDOH Hiroshi

Crystal Growth and Design 9 ( 7 ) 3119-3123 2009.05

Research paper (scientific journal), Joint Work, Accepted

Combined structure analyses of STM and surface-XAFS for self-assembly of metal-thiolate complex: hexanethiolate on Cu(111)

KONDOH Hiroshi

J. Elec. Spectrosc. Relat. Phenom. 172 ( 1-3 ) 88-94 2009.05

Research paper (scientific journal), Joint Work, Accepted

In-situ Study of the Catalytic Oxidation of CO on a Pt(110) Surface Using Ambient Pressure X-ray Photoelectron Spectroscopy

KONDOH Hiroshi

Surface Science Letters 603 ( 5 ) L35-L38 2009.03

Research paper (scientific journal), Joint Work, Accepted

Size-controlled Synthesis and Magnetic Studies of Monodisperse FePd Nanoparticles

Yanglong Hou, KONDOH Hiroshi, Toshiaki Ohta

Journal of Nanoscience and Nanotechnology 9 ( 1 ) 202-208 2009.01

Research paper (scientific journal), Joint Work, Accepted

Lattice-work structure of a TiO2(001) surface studied by STM, core-level spectroscopies and DFT calculations

H. ARIGA, T. TANIIKE, H. MORIKAWA, R. TERO, H. KONDOH, Y. IWASAWA

Chem. Phys. Lett. 454   350-354 2008.01

Research paper (scientific journal), Single Work, Accepted