Catalytic Activity of Titanium and Ruthenium Oxide Nanosheets in the Oxygen Reduction Reaction
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.330
Catalytic Activity of Titanium and Ruthenium Oxide Nanosheets in the Oxygen Reduction Reaction Takahiro Saida1, 2, Miyu Mashiyama2, and Takahiro Maruyama1, 2 1
Department of Applied Chemistry, Faculty of Science and Technology, Meijo University, 1-501 Shiogamaguchi, Tempaku, Aichi, Nagoya 468-8502 Japan
2
Division of Applied Chemistry, Graduate School of Science and Technology, Meijo University, 1-501 Shiogamaguchi, Tempaku, Aichi, Nagoya 468-8502 Japan
Abstract:
Monolayer molecular electrodes composed of titanium oxide nanosheets (TiO2ns) or ruthenium oxide nanosheets (RuO2ns) were prepared and their activities in the oxygen reduction reaction (ORR) were evaluated to investigate the ORR active sites in oxide catalysts. In TiO2ns, the influence of physical distortion sites in the crystal structure formed by introducing oxygen vacancies was determined. The ORR activity of TiO2ns was improved by introducing physical distortion sites. In RuO2ns, the effects of both the type of crystal structure and electrochemical distortion sites arising from redox reactions on ORR performance were studied. The type of crystal structure had almost no effect on ORR activity. In contrast, electrochemical distortion sites were expected to behave as the ORR active sites because the on-set potential of the ORR was similar to the redox peak position for the RuO2ns. Thus, the distortion sites in oxide crystal structures may behave as the active sites in the ORR independent of the metal species.
INTRODUCTION: Polymer electrolyte fuel cells (PEFCs) are attractive as a next-generation power sources for smart grids. Although PEFCs are now commercially available for personal use, their widespread application has not yet been realized. This is because of the high price of PEFCs, which results from their use of platinum as the electrocatalyst. Metal oxide catalysts are a possible solution to this problem. Metal oxide catalysts have high natural abundance and durability compared with the case for practical platinum-based catalysts. In other words, PEFCs will become cheap if they contain metal oxide catalysts. 1851
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Thus, metal oxide catalysts are desirable as next-generation electrocatalysts for PEFCs. However, the activity of metal oxide catalysts in the oxygen reduction reaction (ORR) is lower than that of practical platinum-based catalysts. Many researchers have developed new oxide catalysts, but their activity has still not reached that of conventional carbonsupported platinum [1, 2]. Understanding the reaction mechanism, including the active site and reaction path, is important to enhance the ORR activity of metal oxide catalysts. Many researchers have proposed that the active site of the ORR is oxygen vacancies at the oxide sur
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