Effect of CeO2 morphology on the catalytic properties of Au/CeO2 for base-free glucose oxidation

Abstract

Catalytic selective oxidation of glucose into value-added gluconic acid is one of the sustainable routes for biomass utilization, for which supported Au catalysts have been widely explored. Au/CeO₂ was recently reported as a promising catalyst for glucose oxidation under base-free conditions. However, its catalytic activity needs to be improved with a deep understanding of the catalytic mechanism. Herein, three kinds of CeO₂ supports with different shapes (nanorod, nanocube, nanooctahedra) and exposed facets are synthesized, and the interaction between Au and the supports has been intensively investigated. When applied to base-free selective oxidation of glucose to gluconic acid, the Au/CeO₂ nanorod (R-CeO₂) catalyst delivers the highest catalytic activity with a glucose conversion of 79.6% and gluconic acid selectivity of 100%, due to the strong metal–support interaction and abundant oxygen vacancies. Specifically, the kinetic experiments show that Au/R-CeO₂ remarkably lowers the apparent activation energy for glucose oxidation. Moreover, kinetic isotope effect experiments reveal that R-CeO₂ accelerates the activation and dissociation of water into surface-active hydroxyls, which promote the glucose oxidation reaction even when the Au particles are poisoned by the large amount of gluconic acid. The results demonstrate the significant influence of CeO₂ morphology on the gold catalyst and provide insights into the rational design of high-performance catalysts for glucose oxidation.