Water-mediated proton hopping on an iron oxide surface |
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Authors: | Merte Lindsay R Peng Guowen Bechstein Ralf Rieboldt Felix Farberow Carrie A Grabow Lars C Kudernatsch Wilhelmine Wendt Stefan Lægsgaard Erik Mavrikakis Manos Besenbacher Flemming |
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Institution: | Interdisciplinary Nanoscience Center and Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark. |
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Abstract: | The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H(3)O(+)-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO(2)(110), where water dissociation is a key step in proton diffusion. |
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