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Step Site-Specific Semihydrogenation of Acetylene on the Au Surface
Zongfang Wu1, Fang Wang2, Guanghui Sun1
1Hefei National Laboratory for Physical Sciences at the Microscale, Collaborative Innovation Center of Chemistry for Energy Materials, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, P. R. China.
Abstract:
Supported Au catalysts are highly selective and size-sensitive in catalytic hydrogenation of alkynes under mild conditions. Using thermal-programmed desorption and density functional theory calculations, we study the hydrogenation reactions of C2 hydrocarbons with atomic H and clarify the site-specific selective hydrogenation of C2H2 on Au(997) at low temperatures. On atomic H(a) covered Au(997), hydrogenation of C2H2 goes with 100% selectivity to C2H4 at steps, yet no hydrogenation occurs at terraces; adsorbed C2H4 on neither steps nor terraces reacts with H(a). DFT calculations suggest that the increased adsorption free energies and appropriate reaction barriers of C2 species at steps lead to the step-site specific semihydrogenation of C2H2. These results elucidate the elementary surface reactions between C2 hydrocarbons and atomic H on Au surfaces at the molecular level and significantly deepen the fundamental understanding of the unique selectivity of Au catalysts.
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