Faculty Profiles - NAGAOKA Katsutoshi

Papers - NAGAOKA Katsutoshi

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Influence of the Crystal Structure of Titanium Oxide on the Catalytic Activity of Rh/TiO2 in Steam Reforming of Propane at Low Temperature Reviewed

Yu Lin, Sato Katsutoshi, Toriyama Takaaki, Yamamoto Tomokazu, Matsumura Syo, Nagaoka Katsutoshi

CHEMISTRY-A EUROPEAN JOURNAL Vol. 24 ( 35 ) page： 8742-8746 2018.6

Efficient ammonia synthesis over a Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at high temperature

Yuta Ogura, Katsutoshi Sato, Shin-Ichiro Miyahara, Yukiko Kawano, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Saburo Hosokawa, Katsutoshi Nagaoka

Chemical Science Vol. 9 ( 8 ) page： 2230 - 2237 2018.2

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry

Ammonia is an important feedstock for producing fertiliser and is also a potential energy carrier. However, the process currently used for ammonia synthesis, the Haber-Bosch process, consumes a huge amount of energy
therefore the development of new catalysts for synthesising ammonia at a high rate under mild conditions (low temperature and low pressure) is necessary. Here, we show that Ru/La0.5Ce0.5O1.75 pre-reduced at an unusually high temperature (650 °C) catalysed ammonia synthesis at extremely high rates under mild conditions
specifically, at a reaction temperature of 350 °C, the rates were 13.4, 31.3, and 44.4 mmol g-1 h-1 at 0.1, 1.0, and 3.0 MPa, respectively. Kinetic analysis revealed that this catalyst is free of hydrogen poisoning under the conditions tested. Electron energy loss spectroscopy combined with O2 absorption capacity measurements revealed that the reduced catalyst consisted of fine Ru particles (mean diameter &lt
2.0 nm) that were partially covered with partially reduced La0.5Ce0.5O1.75 and were dispersed on a thermostable support. Furthermore, Fourier transform infrared spectra measured after N2 addition to the catalyst revealed that N2 adsorption on Ru atoms that interacted directly with the reduced La0.5Ce0.5O1.75 weakened the NN bond and thus promoted its cleavage, which is the rate-determining step for ammonia synthesis. Our results indicate that high-temperature pre-reduction of this catalyst, which consists of Ru supported on a thermostable composite oxide with a cubic fluorite structure and containing reducible cerium, resulted in the formation of many sites that were highly active for N2 reduction by hydrogen.

DOI： 10.1039/c7sc05343f

Facile Synthesis of Size-controlled Rh Nanoparticles via Microwave-assisted Alcohol Reduction and Their Catalysis of CO Oxidation

Yoshihide Nishida, Katsutoshi Sato, Tomokazu Yamamoto, Dongshuang Wu, Kohei Kusada, Hirokazu Kobayashi, Syo Matsumura, Hiroshi Kitagawa, Katsutoshi Nagaoka

CHEMISTRY LETTERS Vol. 46 ( 8 ) page： 1254 - 1257 2017.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Size-controlled Rh nanoparticles stabilized by poly(vinylpyrrolidone) were quickly synthesized via alcohol reduction. Microwave-assisted synthesis in closed vessels allowed alcohols with low-to-high boiling points to be used as reductants under the same preparation conditions. Pure ethanol has not been used previously because its boiling point is lower than the temperature required for Rh3+ reduction. Alcohols with relatively strong reduction ability were found to lead to smaller Rh nanoparticles. The ability to oxidize CO was enhanced as the Rh particle size decreased.

DOI： 10.1246/cl.170440

Solid-Solution Alloying of Immiscible Ru and Cu with Enhanced CO Oxidation Activity Reviewed

Bo Huang, Hirokazu Kobayashi, Tomokazu Yamamoto, Syo Matsumura, Yoshihide Nishida, Katsutoshi Sato, Katsutoshi Nagaoka, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 139 ( 13 ) page： 4643 - 4646 2017.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

We report on novel solid-solution alloy nanoparticles (NPs) of Ru and Cu that are completely immiscible even above melting point in bulk phase. Powder X-ray diffraction, scanning transmission electron microscopy, and energy-dispersive X-ray measurements demonstrated that Ru and Cu atoms were homogeneously distributed in the alloy NPs. Ru0.5Cu0.5 NPs demonstrated higher CO oxidation activity than fcc-Ru NPs, which are known as one of the best monometallic CO oxidation catalysts.

DOI： 10.1021/jacs.7b01186

Other Link： http://orcid.org/0000-0003-1774-1537

Carbon-free H-2 production from ammonia triggered at room temperature with an acidic RuO2/gamma-Al2O3 catalyst Reviewed

Katsutoshi Nagaoka, Takaaki Eboshi, Yuma Takeishi, Ryo Tasaki, Kyoko Honda, Kazuya Imamura, Katsutoshi Sato

SCIENCE ADVANCES Vol. 3 ( 4 ) page： e1602747 2017.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER ASSOC ADVANCEMENT SCIENCE

Ammonia has been suggested as a carbon-free hydrogen source, but a convenient method for producing hydrogen from ammonia with rapid initiation has not been developed. Ideally, this method would require no external energy input. We demonstrate hydrogen production by exposing ammonia and O-2 at room temperature to an acidic RuO2/gamma-Al2O3 catalyst. Because adsorption of ammonia onto the catalyst is exothermic, the catalyst bed is rapidly heated to the catalytic ammonia autoignition temperature, and subsequent oxidative decomposition of ammonia produces hydrogen. A differential calorimeter combined with a volumetric gas adsorption analyzer revealed a large quantity of heat evolved both with chemisorption of ammonia onto RuO2 and acidic sites on the gamma-Al2O3 and with physisorption of multiple ammonia molecules.

DOI： 10.1126/sciadv.1602747

Supported Ni catalysts prepared from hydrotalcite-like compounds for the production of hydrogen by ammonia decomposition Reviewed

Katsutoshi Sato, Naruhiko Abe, Takafumi Kawagoe, Shin-ichiro Miyahara, Kyoko Honda, Katsutoshi Nagaoka

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY Vol. 42 ( 10 ) page： 6610 - 6617 2017.3

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Ni catalysts with high surface areas were prepared from Mg-Al hydrotalcite-like compounds containing Ni with different Mg-to-Al ratios for the production of hydrogen via ammonia decomposition. At atomic ratios of Mg-to-Al from 3:1 to 6:1, Ni reduction was greater than 90%, and the amounts of Ni-0 exposed were kept at more than 200 mu mol g(-1). With the increase in Mg-to-Al ratio, turnover frequency was increased due to an increase in the basicity of the support. Of the catalysts examined, Ni_MgAl(6:1) exhibited the highest NH3 conversion, which was attributed to its relatively high basicity and large amount of Ni exposed. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2016.11.150

Other Link： http://orcid.org/0000-0003-1774-1537

Electronic Structure Evolution with Composition Alteration of RhxCuy Alloy Nanoparticles

Natalia Palina, Osami Sakata, L. S. R. Kumara, Chulho Song, Katsutoshi Sato, Katsutoshi Nagaoka, Tokutaro Komatsu, Hirokazu Kobayashi, Kohei Kusada, Hiroshi Kitagawa

SCIENTIFIC REPORTS Vol. 7 ( 7 ) page： 41264 2017.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

The change in electronic structure of extremely small RhxCuy alloy nanoparticles (NPs) with composition variation was investigated by core-level (CL) and valence-band (VB) hard X-ray photoelectron spectroscopy. A combination of CL and VB spectra analyses confirmed that intermetallic charge transfer occurs between Rh and Cu. This is an important compensation mechanism that helps to explain the relationship between the catalytic activity and composition of RhxCuy alloy NPs. For monometallic Rh and Rh-rich alloy (Rh0.77Cu0.23) NPs, the formation of Rh surface oxide with a non-integer oxidation state (Rh(3-delta)+) resulted in high catalytic activity. Conversely, for alloy NPs with comparable Rh: Cu ratio (Rh0.53Cu0.47 and Rh0.50Cu0.50), the decreased fraction of catalytically active Rh(3-delta)+ oxide is compensated by charge transfer from Cu to Rh. As a result, ensuring negligible change in the catalytic activities of the NPs with comparable Rh: Cu ratio to those of Rh-rich and monometallic Rh NPs.

DOI： 10.1038/srep41264

A low-crystalline ruthenium nano-layer supported on praseodymium oxide as an active catalyst for ammonia synthesis Reviewed

Katsutoshi Sato, Kazuya Imamura, Yukiko Kawano, Shin-ichiro Miyahara, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Nagaoka

CHEMICAL SCIENCE Vol. 8 ( 1 ) page： 674 - 679 2017.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Ammonia is a crucial chemical feedstock for fertilizer production and is a potential energy carrier. However, the current method of synthesizing ammonia, the Haber-Bosch process, consumes a great deal of energy. To reduce energy consumption, a process and a substance that can catalyze ammonia synthesis under mild conditions (low temperature and low pressure) are strongly needed. Here we show that Ru/Pr2O3 without any dopant catalyzes ammonia synthesis under mild conditions at 1.8 times the rates reported with other highly active catalysts. Scanning transmission electron micrograph observations and energy dispersive X-ray analyses revealed the formation of low-crystalline nano-layers of ruthenium on the surface of Pr2O3. Furthermore, CO2 temperature-programmed desorption revealed that the catalyst was strongly basic. These unique structural and electronic characteristics are considered to synergistically accelerate the rate-determining step of NH3 synthesis, cleavage of the N N bond. We expect that the use of this catalyst will be a starting point for achieving efficient ammonia synthesis.

DOI： 10.1039/c6sc02382g

Other Link： http://orcid.org/0000-0003-1774-1537

First-Principles Calculation, Synthesis, and Catalytic Properties of Rh-Cu Alloy Nanoparticles Reviewed

Tokutaro Komatsu, Hirokazu Kobayashi, Kohei Kusada, Yoshiki Kubota, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Sato, Katsutoshi Nagaoka, Hiroshi Kitagawa

CHEMISTRY-A EUROPEAN JOURNAL Vol. 23 ( 1 ) page： 57 - 60 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

The first synthesis of pure Rh1-xCux solid-solution nanoparticles is reported. In contrast to the bulk state, the solid-solution phase was stable up to 750 degrees C. Based on facile density-functional calculations, we made a prediction that the catalytic activity of Rh1-xCux can be maintained even with 50 at% replacement of Rh with Cu. The prediction was confirmed for the catalytic activities on CO and NOx conversions.

DOI： 10.1002/chem.201604286

Other Link： http://orcid.org/0000-0003-1774-1537

Catalyst using Pd-Ru solid solution alloy fine particles Reviewed

Kitagawa Hiroshi, Kusada Kohei, Nagaoka Katsutoshi, Sato Katsutoshi, Kutubi M, Shahajahan

2016.9

A Synthetic Pseudo-Rh: NOx Reduction Activity and Electronic Structure of Pd-Ru Solid-solution Alloy Nanoparticles Reviewed

Katsutoshi Sato, Hiroyuki Tomonaga, Tomokazu Yamamoto, Syo Matsumura, Nor Diana Binti Zulkifli, Takayoshi Ishimoto, Michihisa Koyama, Kohei Kusada, Hirokazu Kobayashi, Hiroshi Kitagawa, Katsutoshi Nagaoka

SCIENTIFIC REPORTS Vol. 6 ( 6 ) page： 28265 2016.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Rh is one of the most important noble metals for industrial applications. A major fraction of Rh is used as a catalyst for emission control in automotive catalytic converters because of its unparalleled activity toward NOx reduction. However, Rh is a rare and extremely expensive element; thus, the development of Rh alternative composed of abundant elements is desirable. Pd and Ru are located at the right and left of Rh in the periodic table, respectively, nevertheless this combination of elements is immiscible in the bulk state. Here, we report a Pd-Ru solid-solution-alloy nanoparticle (PdxRu1-x NP) catalyst exhibiting better NOx reduction activity than Rh. Theoretical calculations show that the electronic structure of Pd0.5Ru0.5 is similar to that of Rh, indicating that Pd0.5Ru0.5 can be regarded as a pseudo-Rh. Pd0.5Ru0.5 exhibits better activity than natural Rh, which implies promising applications not only for exhaust-gas cleaning but also for various chemical reactions.

DOI： 10.1038/srep28265

Other Link： http://orcid.org/0000-0003-1774-1537

Dual Lewis Acidic/Basic Pd0.5Ru0.5-Poly(N-vinyl-2-pyrrolidone) Alloyed Nanoparticle: Outstanding Catalytic Activity and Selectivity in Suzuki-Miyaura Cross-Coupling Reaction Reviewed

Md. Shahajahan Kutubi, Katsutoshi Sato, Kenji Wada, Tomokazu Yamamoto, Syo Matsumura, Kohei Kusada, Hirokazu Kobayashi, Hiroshi Kitagawa, Katsutoshi Nagaoka

CHEMCATCHEM Vol. 7 ( 23 ) page： 3887 - 3894 2015.12

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

This article anticipates the development of dual Lewis acidic/basic alloyed nanoparticle (NP) of poly(N-vinyl-2-pyrrolidone)stabilized Pd0.5Ru0.5 solid solution, revealing equivalent Pd delta+ and Ru-delta on the NP surface. This unsupported NP disclosed excellent catalytic efficiency with high turnover frequency, 15000 h(-1) in Suzuki-Miyaura cross-coupling under notable drop of both Pd loading (0.08 mol%) and time (5 min) in air, attributed for its bifunctional acidic/basic modes. The bifunctional modes exposed the most interesting new reaction mechanism ascribed by the inductive effects of p-substituents in arylboronic acid, accelerated reactivity by electron-withdrawing group, revealing an opposite reactivity trend relative to other Pd-based catalysts. Besides, the significant drops of Pd loading and reaction time impeded the metal leaching associated with no changes in NP surface composition/structure after the 3rd cycle (>99% efficiency), revealing a line-up for this NP in the environmental sustainability.

DOI： 10.1002/cctc.201500758

Other Link： http://orcid.org/0000-0003-1774-1537

Development of Efficient Cold-start Process for Oxidative Reforming of n-Butane for Fuel Cell Applications Reviewed

Katsutoshi Nagaoka, Katsutoshi Sato

JOURNAL OF THE JAPAN PETROLEUM INSTITUTE Vol. 58 ( 5 ) page： 274 - 284 2015.9

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN PETROLEUM INST

Efficient cold-start process of hydrogen production by oxidative reforming (OR) of hydrocarbon was developed using Rh catalyst supported on carriers with redox properties. In this process, the heat generated by re-oxidation of reduced catalyst rapidly heats the catalyst from ambient temperature to the catalytic auto-ignition temperature of the OR. OR was triggered at ambient temperature over Rh/CeO2 after reduction at 873 K, but not over Rh catalysts supported on Pr6O11 and Tb4O7, oxides of rare earth elements with redox characters like cerium. Over the latter catalysts, reduction of the carrier occurred at lower temperatures than over CeO2, but the reduced oxides were not re-oxidized at ambient temperature. Our results emphasized that re-oxidation as well as reduction of the catalyst are the key characteristics of the carrier for triggering OR at ambient temperature. With the use of Rh/Ce0.5Zr0.5O2 with excellent redox properties at low temperature, triggering OR of hydrocarbons at ambient temperature was achieved even under non-adiabatic conditions, where heat losses occur, over the catalyst after reduction at 373 K and after in-situ reduction by hydrogen formed during the OR. This new catalytic process is expected to be useful for the development of self-sufficient reforming processes for a new generation of fuel cells.

DOI： 10.1627/jpi.58.274

Other Link： http://orcid.org/0000-0003-1774-1537

Influence of basic dopants on the activity of Ru/Pr6O11 for hydrogen production by ammonia decomposition Reviewed

Katsutoshi Nagaoka, Takaaki Eboshi, Naruhiko Abe, Shin-ichiro Miyahara, Kyoko Honda, Katsutoshi Sato

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY Vol. 39 ( 35 ) page： 20731 - 20735 2014.12

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Basic oxides such as alkali metal oxides, alkaline earth metal oxides, and rare earth oxides were added to Ru/Pr6O11, and the activity of the catalysts with respect to hydrogen production by ammonia decomposition was investigated. Ru/Pr6O11 doped with alkali metal oxides, except for Li2O, achieved higher NH3 conversions than bare Ru/Pr6O11 center dot Cs2O, the most basic of the alkali metal oxides, was the most effective dopant. In contrast, other dopants with lower basicity than the alkali metal oxides achieved lower NH3 conversions than bare Ru/Pr6O11. Changing the Cs/Ru molar ratio revealed that the best Cs/Ru ratio was 0.5-2; the reaction was effectively promoted without negative effects from coverage of the Ru surface by the Cs2O. Varying the order of loading the Ru and Cs2O onto Pr6O11 revealed that loading Ru onto Cs2O/Pr6O11 was an effective way to enhance NH3 conversion, and coverage of the Ru surface was reduced. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2014.07.142

Other Link： http://orcid.org/0000-0003-1774-1537

Inhibition of Ammonia Poisoning by Addition of Platinum to Ru/alpha-Al2O3 for Preferential CO Oxidation in Fuel Cells Reviewed

Katsutoshi Sato, Sho Yagi, Shuhei Zaitsu, Godai Kitayama, Yuto Kayada, Kentaro Teramura, Yusaku Takita, Katsutoshi Nagaoka

CHEMSUSCHEM Vol. 7 ( 12 ) page： 3264 - 3267 2014.12

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

In polymer electrolyte fuel cell (PEFC) systems, small amounts of ammonia (NH3) present in the reformate gas deactivate the supported ruthenium catalysts used for preferential oxidation (PROX) of carbon monoxide (CO). In this study, we investigated how the addition of a small amount of platinum to a Ru/alpha-Al2O3 catalyst (Pt/Ru=1:9 w/w) affected the catalyst's PROX activity in both the absence and the presence of NH3 (130 ppm) under conditions mimicking the reformate conditions during steam reforming of natural gas. The activity of undoped Ru/alpha-Al2O3 decreased sharply upon addition of NH3, whereas Pt/Ru/alpha-Al2O3 exhibited excellent PROX activity even in the presence of NH3. Ruthenium K-edge X-ray absorption near-edge structure (XANES) spectra indicated that in the presence of NH3, some of the ruthenium in the undoped catalyst was oxidized in the presence of NH3, whereas ruthenium oxidation was not observed with Pt/Ru/alpha-Al2O3. These results suggest that ruthenium oxidation is retarded by the platinum, so that the catalyst shows high activity even in the presence of NH3.

DOI： 10.1002/cssc.201402583

Other Link： http://orcid.org/0000-0003-1774-1537

Synthesis and catalytic application of PVP-coated Ru nanoparticles embedded in a porous metal-organic framework Reviewed

Masaaki Sadakiyo, Masaru Kon-no, Katsutoshi Sato, Katsutoshi Nagaoka, Hidetaka Kasai, Kenichi Kato, Miho Yamauchi

DALTON TRANSACTIONS Vol. 43 ( 29 ) page： 11295 - 11298 2014.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

A hybrid catalyst consisting of polymer-coated Ru nanoparticles (Ru-PVP, PVP: poly(N-vinyl-2-pyrrolidone)) embedded in a porous metal-organic framework of ZIF-8 (Ru-PVP@ZIF-8) was synthesized by the crystallization of ZIF-8 in a methanol solution of Ru-PVP. The structural properties of Ru-PVP@ZIF-8 were examined by N-2 gas adsorption, infrared spectra, and X-ray powder diffraction measurements. We successfully identified the most appropriate pretreatment conditions for surface activation of the Ru nanoparticles in the catalyst. The pretreated Ru-PVP@ZIF-8 was applied for a CO oxidation reaction with H-2 gas feeds. Ru-PVP@ZIF-8 was found to exhibit higher catalytic activities and higher CO2 selectivity than those observed on a carbon-supported Ru-PVP (Ru-PVP/C), implying that the pores of the ZIF-8 provide a more suitable environment for the reaction with O-2 and CO gases.

DOI： 10.1039/c4dt00996g

Other Link： http://orcid.org/0000-0003-1774-1537

Effect of the Nature of the CeO2 Support of the Rh Catalyst on Triggering the Oxidative Reforming of n-Butane for H2 Production from Ambient Temperature Reviewed

Katsutoshi Sato, Kouhei Adachi, Yusaku Takita, Katsutoshi Nagaoka

CHEMCATCHEM Vol. 6 ( 3 ) page： 784 - 789 2014.3

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Three Rh catalysts supported on CeO2 with different specific surface areas and redox properties were prepared and evaluated for their ability to trigger the oxidative reforming of n-butane from ambient temperature (approximate to 300K). The reference CeO2 catalysts supplied by the Catalyst Society of Japan (JRC-CEO-1, -3, and -4) were used as supports. Temperature-programmed reduction and O-2 titration measurements over the reduced catalysts indicated that a high number of surface CeO2 sites that were reducible below 573K were present on the Rh/CEO-3 catalyst; this catalyst had the largest specific surface area, and it generated sufficient heat by oxidizing CeO2-x [H(298K)=-368kJ; x=0.5] after H-2 reduction at 773K. Furthermore, the temperature-programmed reactions revealed that forming fine Rh particles on the high surface area of CEO-3 lowers the autoignition temperature (498K) of the oxidative reforming of n-butane because the number of exposed Rh sites initiating reactions between n-butane and O-2 is large. Thus, the Rh/CEO-3 catalyst could trigger the oxidative reforming of n-butane at ambient temperature after H-2 reduction at 773K owing to the heat generated by the spontaneous oxidation of CeO2-x. In contrast, other catalysts could not trigger the reaction after reduction at the same temperature.

DOI： 10.1002/cctc.201300826

Other Link： http://orcid.org/0000-0003-1774-1537

Solid Solution Alloy Nanoparticles of Immiscible Pd and Ru Elements Neighboring on Rh: Changeover of the Thermodynamic Behavior for Hydrogen Storage and Enhanced CO-Oxidizing Ability Reviewed

Kohei Kusada, Hirokazu Kobayashi, Ryuichi Ikeda, Yoshiki Kubota, Masaki Takata, Shoichi Toh, Tomokazu Yamamoto, Syo Matsumura, Naoya Sumi, Katsutoshi Sato, Katsutoshi Nagaoka, Hiroshi Kitagawa

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 136 ( 5 ) page： 1864 - 1871 2014.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

PdxRu1-x solid solution alloy nanoparticles were successfully synthesized over the whole composition range through a chemical reduction method, although Ru and Pd are immiscible at the atomic level in the bulk state. From the XRD measurement, it was found that the dominant structure of PdxRu1-x changes from fcc to hcp with increasing Ru content. The structures of PdxRu1-x nanoparticles in the Pd composition range of 30-70% consisted of both solid solution fcc and hcp structures, and both phases coexist in a single particle. In addition, the reaction of hydrogen with the PdxRu1-x nanoparticles changed from exothermic to endothermic as the Ru content increased. Furthermore, the prepared PdxRu1-x nanoparticles demonstrated enhanced CO-oxidizing catalytic activity; Pd0.5Ru0.5 nanoparticles exhibit the highest catalytic activity. This activity is much higher than that of the practically used CO-oxidizing catalyst Ru and that of the neighboring Rh, between Ru and Pd.

DOI： 10.1021/ja409464g

Other Link： http://orcid.org/0000-0003-1774-1537

Cr3+-Co0.054Ni0.018Mg0.93O Solid-Solution Catalysts for High-Pressure Syngas Production: Effect of Chromium on the Reduction and Catalysis Reviewed

Katsutoshi Nagaoka, Yosuke Abe, Yusaku Hashimoto, Takahiro Ishikawa, Katsutoshi Sato, Yusaku Takita, Toshiya Wakatsuki, Masahiro Kunisu, En Suda, Shin Inamoto

ACS CATALYSIS Vol. 3 ( 7 ) page： 1564 - 1572 2013.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Adding Cr to heat-tolerant Co0.054Ni0.018Mg0.93O solid-solution catalysts for CH4/CO2/H2O reforming at 2.1 M.Pa allowed us to control the key properties determining the behavior of the supported catalysts, such as the reduction degree of the metal, metal particle size, and amount of exposed zerovalent metals. A small load of Cr [Cr/(Co + Ni) = 0.11 mol %] efficiently catalyzed Co2+ and Ni2+ reduction. This catalyst, which had abundant small alloy particles on the support material, resisted coking and oxidative deactivation, even under accelerated deterioration conditions: X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, extended X-ray absorption fine structure, and scanning transmission electron microscopy energy-dispersive X-ray measurements indicated that Cr existed as a trivalent cation in a CrxCo0.054Ni0.018Mg0.93O1+1.5x solid solution, leading to the formation of a divalent cation vacancy and that Cr3+ was abundant on the surface of the catalyst particles after calcination at 1373 K. The Cr3+ destabilized Co2+ and Ni2+ in the solid solution, especially on the surface of the catalyst particles and, thus, promoted Co2+ and Ni2+ reduction. However, excess Cr3+ induced sintering of the catalyst particles, resulting in aggregation of alloy particles and, thus, in an increased risk of coking.

DOI： 10.1021/cs400199b

Other Link： http://orcid.org/0000-0003-1774-1537

Discovery of Face-Centered-Cubic Ruthenium Nanoparticles: Facile Size-Controlled Synthesis Using the Chemical Reduction Method Reviewed

Kohei Kusada, Hirokazu Kobayashi, Tomokazu Yamamoto, Syo Matsumura, Sumi Naoya, Katsutoshi Sato, Katsutoshi Nagaoka, Yoshiki Kubota, Hiroshi Kitagawa

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 135 ( 15 ) page： 5493 - 5496 2013.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

We report the first discovery of pure face-centered-cubic (fcc) Ru nanoparticles. Although the fcc structure does not exist in the bulk Ru phase diagram, fcc Ru was obtained at room temperature because of the nanosize effect. We succeeded in separately synthesizing uniformly sized nanoparticles of both fcc and hcp Ru having diameters of 2-5.5 nm by simple chemical reduction methods with different metal precursors. The prepared fcc and hcp nanoparticles were both supported on gamma-Al2O3, and their catalytic activities in CO oxidation were investigated and found to depend on their structure and size.

DOI： 10.1021/ja311261s

Other Link： http://orcid.org/0000-0003-1774-1537

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