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A Single-metal site Pt-O(OH) x Catalyzes the Low-temperature Water-gas Shift Reaction

X19A. A Single-metal site Pt-O(OH) x Catalyzes the Low-temperature Water-gas Shift Reaction.

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A Single-metal site Pt-O(OH) x Catalyzes the Low-temperature Water-gas Shift Reaction

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  1. X19A A Single-metal site Pt-O(OH)x Catalyzes the Low-temperature Water-gas Shift Reaction Yanping Zhai1, Danny Pierre1, Rui Si1, Weiling Deng1, Peter Ferrin2, Anand U. Nilekar2, Guowen Peng2, Jeffrey A. Herron2, David C. Bell3, Howard Saltsburg1, Manos Mavrikakis2, Maria Flytzani-Stephanopoulos1 1. Tufts University, 2. University of Wisconsin, Madison, 3. Harvard University • Alkali ions (Na or K) added in small amounts activate platinum adsorbed on Al2O3 or SiO2 for the low-temperature WGS reaction used for producing H2. Both experimental evidence and DFT calculations suggest that a partially oxidized Pt-alkali-Ox(OH)y species is the active site for the low-temperature Pt-catalyzed WGS reaction. • The catalytic site is support-independent. We show it on Al2O3 and on SiO2 , the latter being the most inert of oxide supports for the Pt-catalyzed WGS reaction. Without the alkali promoter, Pt-SiO2 is totally inactive. With it, the catalyst is of comparable activity to Pt-CeO2, one of the best known low-temperature shift catalysts. • These findings are useful for the design of highly active and stable WGS catalysts that contain only trace amounts of a precious metal without the need for a reducible oxide support such as ceria. In order for a Pt atom to become active for the WGS reaction, it must be stabilized in an oxidized form and be surrounded by O and OH groups. To avoid the usual implication of the support in the mechanism, we examined inert supports, and as source of OH species we used the alkali ions. The alkali ion–associated surface OH groups are activated by CO at low temperatures (~100°C) in the presence of atomically dispersed platinum. Yanping Zhai, Danny Pierre, Rui Si, Weiling Deng, Peter Ferrin, Anand U. Nilekar, Guowen Peng, Jeffrey A. Herron, David C. Bell, Howard Saltsburg, Manos Mavrikakis, and Maria Flytzani-Stephanopoulos, “Alkali-Stabilized Pt-OHx Species Catalyze Low-Temperature Water-Gas Shift Reactions” Science, 329, 1633 (2010). Work performed on beamline X19A.

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