Propene Epoxidation with H₂/H₂O/O₂ Mixtures Over Gold Atoms Supported on Defective Graphene: A Theoretical Study

The mechanism of propene epoxidation by H2/H2O/O2 mixtures catalyzed by gold atoms supported on defective graphene has been investigated by means of periodic density functional theory (DFT) calculations. The fact of being isolated and yet strongly bound to the support gold atoms makes formation of gold hydroperoxide H–Au–OOH intermediates from H2 and O2 barrierless and the subsequent reaction with propene yielding propene oxide (PO) and H2O thermodynamically and kinetically favored. The main advantage of the Au/graphene material explored in this work is not related to catalyst activity but to the selectivity toward PO that is greatly enhanced due to suppression of the main competing routes. Thus, neither propene hydrogenation yielding propane nor O2 dissociation finally resulting in acrolein formation and/or propene combustion can compete with the desired epoxidation. The present results suggest a promising route to prepare active and highly selective gold-based catalysts for propene epoxidation