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Theoretical study of small clusters Au<inf>5-6</inf> on Au/SAPO-11 catalysts and their interactions with CO

Abstract:

Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au5/SAPO-11, Au 6/SAPO-11, CO-Au5/SAPO-11 and CO-Au6/SAPO-11 aggregates to analyze the geometries of small clusters of Au5 and Au6 on SAPO-11 support. Au5 cluster presents a pentagonal structure in Au5/SAPO-11. Au6 aggregate shows a "multi triangular" structure (as from a trapezoidal "W shaped" Au5) in Au6/SAPO-11. Au5 is also obtained as an "X shaped" structure. Similarly another Au6 aggregate configuration is obtained also multi triangular but as from X shape Au5 cluster. The CO interaction with Au5 and Au 6/SAPO-11 is studied. The formation energy ΔEF of the aggregates, the CO adsorption energy ΔEads on them and CO frequency are presented. © 2014-IOS Press.