A Thermally Stable Cr鈥揅u Nanostructure Embedded in the CeO2 Surface as a Substitute for Platinum-Group Metal Catalysts

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• 作者：Hiroshi Yoshida ; Noriko Yamashita ; Shota Ijichi ; Yuri Okabe ; Satoshi Misumi ; Satoshi Hinokuma ; Masato Machida
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：November 6, 2015
• 年：2015
• 卷：5
• 期：11
• 页码：6738-6747
• 全文大小：532K
• ISSN：2155-5435

文摘

High catalytic activities for CO鈥揙₂ and CO鈥揘O reactions that were superior to or comparable with those of platinum-group metal catalysts were achieved by synchronous dual-mode arc plasma deposition of a very small amount of Cr and Cu (0.07 wt % each) onto CeO₂, followed by subsequent thermal aging at 900 掳C for 25 h. The turnover frequency for CO oxidation over Cr鈥揅u/CeO₂ was 3-fold higher than that over Cu/CeO₂ and exceeded values for the Rh, Pd, and Pt catalysts loaded on CeO₂, despite a significant decrease in the surface area from 169 to 5 m² g^鈥? caused by thermal aging. Experimental structure characterization and density functional theory calculations based on CeO₂ (111) surface slab models revealed that Cu⁺ substitution for surface Ce atoms leads to the formation of asymmetric 3-fold oxygen coordination sites capable of efficient CO chemisorption and catalytic activity. In addition, Cr³⁺ was incorporated into the surface structure of CeO₂; it plays an important role in enhancing the surface concentration of Cu⁺. A CO oxidation rate with nearly zero partial orders with respect to O₂ and isotopic C¹⁶O鈥?sup>18O₂ reactions yielding C¹⁶O₂ as the primary product demonstrated that the reaction proceeds via the Mars鈥搗an Krevelen mechanism.