Crystal Faces-Tailored Oxygen Vacancy in Au/CeO2 Catalysts for Efficient Oxidation of HMF to FDCA

Graphical Saving face : Catalytic performance of Au/CeO 2 with different exposed CeO 2 crystal faces for oxidation of 5-hydroxymethlfurural to 2,5-furandicarboxylic acid is dependent on the oxygen vacancy (V O ) concentration. Higher V O concentration of Au/rod-CeO 2 (110) is more beneficial for adsorption of oxygen and formation of active oxygen species than Au/cube-CeO 2 (100) and Au/oct-CeO 2 (111). Developing an efficient catalyst to upgrade 5-hydroxymethylfurfural (HMF) to high-value-added downstream chemicals is of great significance in biomass conversion. Nanorod (110)-, nanocube (100)-, and nanooctaheron (111)-CeO 2 -supported Au nanoparticles were prepared to investigate the intrinsic effect of CeO 2 crystal faces on the oxidation of HMF to 2,5-furandicarboxylic acid (FDCA). The experimental results and density functional theory calculation revealed that the concentration of oxygen vacancy (V O ) for exposed specific crystal faces was crucial to the oxygen adsorption ability, and Au/nanorod-CeO 2 with the highest V O concentration promoted the formation of more oxygen active species (superoxide radical) on CeO 2 (110) crystal face than (100) and (111) crystal faces. Besides, the higher V O concentration could provide a strong adsorption ability of HMF, greatly boosting the activation of HMF. Thus, these results led to a superior catalytic activity for HMF oxidation over Au/nanorod-CeO 2 (FDCA yield of 96.5 %). In-situ Fourier-transform (FT)IR spectroscopy uncovered the HMF oxidation pathway, and the possible catalytic mechanism was proposed. The deep insight into the role of regulation for crystal faces provides a basis for the rational design of highly active facets for the oxidation of HMF and related reactions.