Impact of the Oxygen Vacancies on Copper Electronic State and Activity of Cu‐Based Catalysts in the Hydrogenation of Methyl Acetate to Ethanol

Abstract

Reducible oxides supported copper‐based catalysts have been widely used in ester hydrogenations due to their excellent catalytic performance. However, the role of surface oxygen vacancies is still unclear. Here, we fabricated four copper‐based catalysts using different shaped CeO2 nanocrystals as supports for the hydrogenation of methyl acetate (MA) to ethanol. The catalytic activities significantly changed depending on the morphology of supports in the order of rod>cube>spindle>octahedron, which was in line with the trend of the formation energy of oxygen vacancies on the corresponding exposed lattice planes. Combined with the results of chemisorption and in\u2005situ FTIR experiments, it is demonstrated that the oxygen vacancies are not the primary active sites for MA hydrogenation, whereas they could significantly affect the electronic state of copper species. Under reduced conditions, the mobile oxygens could be released from the lattice and form lots of oxygen vacancies, which could strongly interact with copper particles and benefit for the generation and stabilization of Cu+ species. Thus, increasing the oxygen mobility of supports could effectively increase the amount of surface Cu+ species and enhance the catalytic activity for MA hydrogenation.