Article
Chemistry, Physical
Hiroshi Yoshida, Haruka Oyama, Ryo Shiomori, Taiki Hirakawa, Junya Ohyama, Masato Machida
Summary: The addition of nickel increased the NO reduction activity of Cu/Al2O3 by forming a NiCuAl2O4 solid solution, promoting NO adsorption on Cu+ and accelerating the NO reduction reaction.
Article
Chemistry, Multidisciplinary
Kohei Kusada, Dongshuang Wu, Yusuke Nanba, Michihisa Koyama, Tomokazu Yamamoto, Xuan Quy Tran, Takaaki Toriyama, Syo Matsumura, Ayano Ito, Katsutoshi Sato, Katsutoshi Nagaoka, Okkyun Seo, Chulho Song, Yanna Chen, Natalia Palina, Loku Singgappulige Rosantha Kumara, Satoshi Hiroi, Osami Sakata, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa
Summary: Efforts have been made since 1970 to reduce toxic emissions from automobiles, particularly through the development of more efficient catalysts. Rh has been essential for catalytic NOx reduction, but its sharp price spikes have prompted the search for alternatives. Recent research shows that PdRuM ternary solid-solution alloy nanoparticles can replace Rh and reduce catalyst costs.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Physical
Ben Ma, Zhaohui Chen, Zhuang Lin, Lin Cheng, Yingke Zhou
Summary: This study investigates the effects of Mg doping on the performance of Mn-Cr spinel oxide cathodes in solid oxide fuel cells (SOFCs). Both experimental results and density functional theory (DFT) calculations show that Mg doping can optimize the electronic structure of the spinel oxide, increase the oxygen vacancy concentration, and improve the electrical conductivity and catalytic activity. The Mg-doped Mn-Cr spinel oxide cathode exhibits superior performance with high area-specific polarization resistance and maximum power density.
JOURNAL OF POWER SOURCES
(2023)
Article
Nanoscience & Nanotechnology
Kyoko Fujita, Hiroyuki Asakura, Saburo Hosokawa, Kentaro Teramura, Masaki Kobayashi, Koji Fujita, Tsunehiro Tanaka
Summary: The study revealed that Fe-doped gamma-Al2O3 can store and release oxygen reversibly during catalytic reactions, offering a new approach for developing oxygen storage materials without the need for rare metals.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Nanoscience & Nanotechnology
Taiki Hirakawa, Yushi Shimokawa, Yuma Miyahara, Masayuki Tsushida, Hiroshi Yoshida, Junya Ohyama, Masato Machida
Summary: Ternary FexNiyCu1-x-y metal nanoparticles supported on Al2O3 were investigated as three-way catalysts without precious metals. Near-equimolar catalysts exhibited the highest activity and the highest fraction of metallic states. The presence of Fe-Ni oxide improved the regenerability and stability of metallic-state Cu and Ni species, enhancing the stability of the active metallic state by promoting the oxidative adsorption of C3H6.
ACS APPLIED NANO MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Konstantin Khivantsev, Carlos Garcia Vargas, Jinshu Tian, Libor Kovarik, Nicholas R. Jaegers, Janos Szanyi, Yong Wang
Summary: The atomically dispersed Rh cations on ceria, prepared by a high-temperature atom-trapping synthesis, are shown to be the active species for the (CO+NO) reaction with high turnover frequency at 120 degrees C. In wet conditions, the main products are ammonia and nitrogen above 120 degrees C. The presence of water promotes low-temperature activity and enhances NH3 formation in the reaction.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Physical
Yuhang Wang, Yifei Zhang, Qike Jiang, Song Guo, Alfons Baiker, Gao Li
Summary: The co-doping of ceria with Cu and Cr forming a ternary CuCrCeOx solid solution significantly improves the catalytic performance, N-2 selectivity, and NO/CO conversions. The coupling of different transition metal redox cycles and the surface population of oxygen vacancies contribute to the enhanced activity. The ternary CuCrCeOx catalyst exhibits the highest oxygen defect density and achieves 100% N-2 selectivity at lower temperatures.
Article
Chemistry, Inorganic & Nuclear
Hongli Wu, Weizao Liu, Xiaoyong Jiang, Ya Liang, Chen Yang, Jun Cao, Qingcai Liu
Summary: A novel SiO2@Mn catalyst with a core-shell structure was synthesized using manganese carbonate tailings, which effectively limited SO(2) adsorption and enhanced the catalyst's resistance to SO2. The catalyst exhibited improved N-2 selectivity and increased NH3 adsorption capacity due to the interaction between Mn and Si. Additionally, the formation mechanisms of N2O and the anti-SO2 poisoning mechanism were proposed, and DFT calculations showed that SO(2) preferentially adsorbed onto the SiO2 surface, preventing erosion of active sites.
INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Taiki Hirakawa, Yuma Miyahara, Yushi Shimokawa, Koshi Nishiyama, Masayuki Tsushida, Hiroshi Yoshida, Junya Ohyama, Masato Machida
Summary: In this research, various quaternary metal catalysts were investigated for the replacement of precious metals in three-way catalysts. The CrFeNiCu system demonstrated the best catalytic performance, achieving a lower light-off temperature for CO, C3H6, and NO compared to a reference catalyst. Structural analysis revealed that the catalyst underwent structural changes during the catalytic reaction. The presence of Cr oxide significantly enhanced CO/C3H6 oxidation and promoted the regeneration of the active NiCu metallic surface for NO reduction.
Article
Chemistry, Inorganic & Nuclear
Guike Zhang, Fuzhou Wang, Yuying Wan, Yali Guo, Ke Chu
Summary: We demonstrate iron diboride (FeB2) as an efficient metal diboride catalyst for electrochemical NO-to-NH3 reduction (NORR), showing high NH3 yield rate and Faradaic efficiency. The synergy between Fe and B sites activates the NO molecule and favors its protonation on B sites. Moreover, Fe and B sites preferentially absorb NO over H atoms, suppressing hydrogen evolution and enhancing NORR.
INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Physical
Mariana B. S. Felgueiras, Joao Restivo, Juliana P. S. Sousa, Manuel F. R. Pereira, Olivia S. G. P. Soares
Summary: Nitrogen oxides (NOx) are pollutants that greatly impact atmospheric contamination and human health. This study focuses on synthesizing structured carbon catalysts with metals and nitrogen groups on their surface, which are catalytically active in reducing NO. The use of structured catalysts offers advantages in terms of thermal stability and pressure drop compared to powder catalysts. The introduction of nitrogen and metals modifies the properties of the catalyst, with copper being identified as the most active transition metal for NO reduction. This work demonstrates the synthesis and application of carbon-supported structured catalysts containing transition metals for NO reduction, as well as the investigation of factors influencing their performance.
Article
Computer Science, Information Systems
Guilong Liu, Yehai Xie, Xiuwei Gao
Summary: Attribute reduction is an important component in rough set theory and formal concept analysis, and the three-way concept lattice is a combination of concept lattices and three-way decision theory. This paper investigates granular reduction and distribution reduction in general formal decision contexts, and proposes reduction algorithms based on discernibility matrix for each type of reduction. The effectiveness of the three-way granular reduction algorithm is evaluated using 17 UCI datasets.
INFORMATION SCIENCES
(2022)
Article
Chemistry, Physical
Li Danyang, Sun Liping, Li Qiang, Xia Tian, Huo Lihua, Zhao Hui
Summary: For the first time, Fe3O4-based high-entropy spinel oxides were studied for the electrochemical production of hydrogen peroxide. Among the substances investigated, (Fe0.2Zn0.2Co0.2Ni0.2Cu0.2) Fe2O4 showed significantly enhanced 2e-ORR electrocatalytic property, with excellent selectivity and durability. The improved performance is attributed to the high concentration of oxygen vacancies on the material surface and the multicomponent co-interaction in the high-entropy oxide.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Multidisciplinary
Kazu Okumura, Sachiko Morita, Hikaru Iiyoshi, Hiromitsu Takaba
Summary: Thermal treatment of Pd nanoparticles or Pd(NH3)(4)(NO3)(2) supported on MgO resulted in the formation of a solid solution of Pd-MgO. The valence of Pd in the Pd-MgO solid solution was determined to be 4+ from the comparison of XANES with reference compounds. The shrinkage of Pd-O bond distance was observed in comparison with that of the nearest-neighboring Mg-O bond in MgO, which agreed with DFT calculations. The dispersion of Pd-MgO showed a two-spike pattern due to the formation and segregation of solid solutions above 1073 K.
Article
Chemistry, Physical
Can Li, Vishnu Sriram, Zhouyang Liu, Dale Brewe, Joo-Youp Lee
Summary: The Mo-V-based SCR catalyst showed good performance for Hg-0 oxidation and NO reduction under various conditions, with the best results observed using anatase TiO2 and a calcination temperature of 500 degrees Celsius. Various characterization techniques were used to investigate the effects of different parameters and conditions on the catalyst performance.
APPLIED CATALYSIS A-GENERAL
(2021)
Article
Chemistry, Applied
Hiroshi Yoshida, Tomoyo Koide, Takuya Uemura, Yusuke Kuzuhara, Junya Ohyama, Masato Machida
Summary: In this study, the surface modification of a nanometric Rh overlayer by a small amount of Ce was found to enhance its three-way catalytic activity. The oxygen storage/release behavior of the surface Ce contributed to buffering the air-to-fuel change and improving the catalytic activity. The Ce-modified Rh overlayer with a metal honeycomb structure exhibited high activity even under A/F perturbation conditions at high space velocity, making it a promising and energy-saving alternative to conventional catalytic converters.
Article
Chemistry, Applied
Takehiro Tamura, Junya Ohyama, Kyoichi Sawabe, Atsushi Satsuma
Summary: The twinned structure of metal nanoparticles can be reversibly controlled by gas treatment, which strongly affects catalysis due to the unique atomic alignment and bond strain in metal nanoparticles. In this study, the structure of supported Ag nanoparticles on Ag/Al2O3 was changed from single crystal to twin structure by subsequent CO gas treatment after H2 treatment. This change in structure enhanced the CO oxidation activity, and the catalytic activity could be reversibly changed by applying H2 and CO gas treatment.
Article
Chemistry, Physical
Ayumi Fujiwara, Yutaro Tsurunari, Shundai Iwashita, Hiroshi Yoshida, Junya Ohyama, Masato Machida
Summary: In three-way catalytic converters, perturbations in exhaust gas composition between fuel-rich and fuel-lean conditions affect catalyst surface and conversion efficiencies. In this study, real-time changes in surface states of Pd-based catalysts were monitored using in situ diffuse reflectance spectroscopy. The oxidation state of Pd fluctuated in sync with the perturbations, with smaller oscillation amplitude on CeO2-ZrO2 (CZ) compared to Al2O3. CZ's oxygen scavenging function buffered oxidative degradation, resulting in higher reaction rates and preventing coke deposition. This study highlights the usefulness of in situ DRS in understanding transient catalytic processes and bridging the gap between on-board performances and laboratory tests.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Nanoscience & Nanotechnology
Mohammad Atiqur Rahman, Junya Yagyu, Md. Saidul Islam, Masahiro Fukuda, Sora Wakamatsu, Ryuta Tagawa, Zhiqing Feng, Yoshihiro Sekine, Junya Ohyama, Shinya Hayami
Summary: Graphene oxide (GO)-based materials have been extensively studied as low-cost efficient solid electrolytes for fuel-cell application. However, the limited proton conductivity of GO in the out-of-plane directions and associated lower fuel-cell performance restrict their practical application. In this study, a sulfate ion-intercalated three-dimensional graphene oxide (3DSGO) with exceptionally high out-of-plane proton conductivity and improved fuel-cell performance was demonstrated.
ACS APPLIED NANO MATERIALS
(2023)
Article
Energy & Fuels
Yuka Tsuchimura, Hiroshi Yoshida, Masato Machida, Shun Nishimura, Keisuke Takahashi, Junya Ohyama
Summary: Cu-CHA exhibits high catalytic performance in the direct oxidation of CH4 to CH3OH. The catalytic activity varies with the composition of Cu-CHA. Three groups of Cu species were identified based on their catalytic performance: low Cu/Al ratio for high selectivity and low activity, medium Cu/Al ratio for high selectivity and high activity in CH3OH production, and high Cu/Al ratio for high activity in complete oxidation of CH4 to CO2. The mono-(mu-oxo) di-Cu species in Cu-CHA is proposed as the active species for the catalytic reaction.
Article
Chemistry, Physical
Masato Machida, Hideto Yoshida, Naoto Kamiuchi, Yasuhiro Fujino, Takeshi Miki, Masaaki Haneda, Yutaro Tsurunari, Shundai Iwashita, Rion Ohta, Hiroshi Yoshida, Junya Ohyama, Masayuki Tsushida
Summary: Under dynamic SLR cycle conditions, the Rh/ZrO2-CeO2 (Rh/ZC) three-way catalyst experienced more severe deactivation compared to static conditions. The complete encapsulation of Rh particles with a ZC overlayer under dynamic SLR cycle conditions led to physical blockage and suppressed catalytic activity. This encapsulation phenomenon was not recovered by post-treatment in air at 1000 degrees C.
Article
Chemistry, Physical
Junya Ohyama, Hideto Ushijima, Takashi Yamashita, Akihiro Yamashita, Hiroshi Yoshida, Masato Machida
Summary: Improving the catalysts for hydrogen oxidation reaction (HOR) in alkaline conditions is crucial for the development of anion exchange membrane fuel cells. Previous studies have shown that Pt catalysts can be enhanced by forming coordinationally saturated surface sites and also by combining Pt with other metals. This study demonstrates the use of Pt-Ni alloy thin films as highly active structures in alkaline HOR, with improved activity compared to Pt monometal thin-film and nanoparticle catalysts.
ACS APPLIED ENERGY MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Masato Machida, Hideto Yoshida, Naoto Kamiuchi, Yasuhiro Fujino, Takeshi Miki, Masaaki Haneda, Yutaro Tsurunari, Shundai Iwashita, Rion Ohta, Hiroshi Yoshida, Junya Ohyama
Summary: This study investigates the performance of catalysts after real engine aging and finds that pre-aged catalysts can maintain better catalytic performance at high temperatures. It is found that the migration of Rh nanoparticles from the ZC surface to the Al2O3 binder interface plays a crucial role in mitigating the encapsulation of Rh nanoparticles by ZC. By using a dual-oxide support formulation, the deterioration extent of the catalyst and the oxygen storage capacity performance can be effectively improved.
ACS APPLIED NANO MATERIALS
(2023)
Review
Chemistry, Physical
Hiroshi Yoshida, Masato Machida
Summary: Although most solid catalysts have a three-dimensional structure of nanoparticles dispersed on a porous support, this structure is not optimal for all catalytic reactions. This article introduces a unique catalytic performance of a two-dimensional metal foil-supported nanometric Rh thin film, which is particularly suitable for CO-NO reaction and three-way catalytic reaction.
Article
Chemistry, Physical
Fumiya Nishino, Hiroshi Yoshida, Masato Machida, Shun Nishimura, Keisuke Takahashi, Junya Ohyama
Summary: Catalysts for oxidative coupling of methane (OCM) were designed through machine learning of the property of surface oxygen species. The CO32- peak energy was chosen as the guiding parameter and important physical quantities determining the CO32- peak energy were identified through machine learning. Synthesized catalysts were found to have high catalytic performance based on their predicted compositions, and a new highly active OCM catalyst was discovered.
CATALYSIS SCIENCE & TECHNOLOGY
(2023)
Article
Chemistry, Physical
Masato Machida, Hideto Yoshida, Naoto Kamiuchi, Yasuhiro Fujino, Takeshi Miki, Masaaki Haneda, Yutaro Tsurunari, Shundai Iwashita, Rion Ohta, Hiroshi Yoshida, Junya Ohyama, Masayuki Tsushida
Summary: A Rh/ZrO2-CeO2 (Rh/ZC) three-way catalyst exhibited more severe deactivation under dynamic SLR cycle conditions compared to static conditions. The total encapsulation of Rh particles by a ZC overlayer led to physical blockage and suppressed catalytic activity. The encapsulation under a dynamic SLR cycle condition suggests the activation of ZC migration near the metal-support interface.
Article
Chemistry, Physical
Hiroki Iwai, Fumiya Nishino, Tomokazu Yamamoto, Masaki Kudo, Masayuki Tsushida, Hiroshi Yoshida, Masato Machida, Junya Ohyama
Summary: Researchers have successfully predicted and removed the background image of supported metal nanoparticles using a deep learning-based image inpainting method. The 3D reconstruction of the extracted images reveals the atomic structure and deformed shape of the nanoparticles, providing insights into their catalytic activity. This study demonstrates the importance of 3D atomic-scale analysis in understanding and designing supported metal catalysts.