2020 Fiscal Year Research-status Report
Ambient-Pressure synchrotron X-ray study to reveal atomic-scale mechanism of CO oxidation and three-way catalytic reaction of Ru based solid-solution nanoparticles
| Project/Area Number |
20K15083
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
徐 玉均 国立研究開発法人物質・材料研究機構, 技術開発・共用部門, NIMSポスドク研究員 (30814206)
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| Project Period (FY) |
2020-04-01 – 2022-03-31
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| Keywords | H absorption / CO oxidation / three-way catalysts / EXAFS / AP-XPS |
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| Outline of Annual Research Achievements |
Rh is a material that does not absorb hydrogen atoms. However, when the particle size of the Rh materials becomes small, hydrogen adsorption on the surface area of the Rh nanoparticles is possible due to surface disordering of the Rh nanoparticles. Besides, as the size of Rh nanoparticles increases, hydrogen adsorption on the Rh nanoparticles occurs less than that of the small size, measured by dispersive XAFS. (RSC Adv.)
The change in the atomic arrangement at the interface on the bimetallic alloy (AgRh and PdPt) nanoparticles were investigated using the in-situ EXAFS measurement under hydrogen conditions.The research results were published in the J. Alloys Compd. and ACS Appl. Mater. Interface as research articles.
AgRh nanoparticles: A substantial fraction of the sample is an alloy phase formed by mixing of nano/sub-nanosized domains of Rh and Ag NPs. Mixing at the atomic level mainly occurs in the interfacial region. Consequently, the interfacial region has an important influence over the microstructure and provides active sites for hydrogen absorption.
PdPt nanoparticles: The Pd K-edge extended X-ray absorption fine structure data indicate that in CS and SS NPs a substantial fraction of the signal derives from Pd－Pd atomic pairs, indicating that Pd clusters remain present even after hydrogen absorptin and desorption process. Hydrogen absorption and desorption process on the PdPt nanoparticles causes a atomic rearrangement of the interfacial structure,which becomes homogeneously distributed.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
In 2020, we have been studied the oxidation and reduction reaction process through dispersive XAFS and in-situ XAFS experiments at Pd K edge, Ru K edge, and Ce L3 edge at 300 and 400 C to investigate the three-way catalysts (lean-rich-stoichiometry conditions) mechanism of PdRu nanoparticles-CeO2ZrO2 (CZ). In addition, we were conducted the in-situ XAFS experiment under CO and CO oxidation conditions at 100, 150, and 200 C to investigate the reaction site of the PdRu nanoparticles-CZ. I am preparing the research articles on the three-way catalytic reactoin of the PdRu nanoparticles-CZ.
To understand the atomic behavior of the PdRu nanoparticles under CO oxidation, ambient pressure XPS (AP-XPS) was performed at Pohang Accelerator Laboratory in Korea. We found the surface segregation of specific atoms during CO, O2, and CO oxidation conditions. Surface segregation of the metal atoms in the alloy nanoparticles is important evidence to know the adsorption sites of metals under the CO oxidation reaction.
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| Strategy for Future Research Activity |
Three-way catalsts: The evaporation of Ru in PdRu nanoparticles is the reason why the three-way catalytic performance of PdRu nanoparticles decreases at high temperatures. To prevent evaporation of Ru at high operation temperature, we synthesized PdRuIr nanoparticles, as a ternary alloy. Kusada et al., reported that the PdRuIr nanoparticles was stable at the high temperature. (Adv. Mater. 33, 2005206 (2021))Therefore, the dispersive XAFS and in-situ XAFS experiments will be conducted to find out the mechanism by which the performance of the ternary PdRuIr nanoparticles increases.
CO oxidation: The AP-XPS experiment will be conducted to investigate the surface atomic behaviors of hcp and fcc structure PtRu nanoparticles under CO oxidation. In addition, we are planning to observe the CO oxidation effect caused by the crystal structure of hcp and fcc structure. Because I cannot go to Pohang Accelerator Laboratory due to COVID 19, the AP-XPS experiment will be performed by a research collaborator.
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| Causes of Carryover |
From April 2021, I moved the research Institute from NIMS to JASRI.
Therefore, I am planning to purchase the equipment for HAXPES beamline and XAFS experiment, including the in-situ equipment. In addition, I am planning to use the other beamtime fee (XAFS beamline) and publication fee of research articles, which related to the research of the metal nanoparticles. Due to COVID 19, it is impossible to participate in experiments and conferences in foreign countries, so I will use the remaining money to develop the in-situ synchrotron X-ray technique equipments.
HAXPES: Sample holder for in-situ experiment, pelletizer
XAFS: Beamtime fee, stainless holder, gas
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Research Products
(11 results)
