Facet-engineered CeO2 with Cu single atoms drives photocatalytic selective oxidation of 5-hydroxymethylfurfural

The crystal facet of CeO2 is crucial in governing the catalytic performance of CeO2. However, studies on the relationship between the photocatalytic oxidation performance of CeO2 and its crystal facets are scarce. Herein, we synthesized a series of CeO2. Through loading Cu single atoms (Cu/CeO2), the facet effects of crystal facets on photocatalytic selective oxidation were systematically studied by employing the selective oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran as a model. Because the (110) facet's superior electron transfer efficiency is feasible for absorbing 5-hydroxymethylfurfural, eliminating α-H, and desorbing 2,5-diformylfuran, the selectivity of Cu/CeO2-nanorods (Cu/CeO2-R) with the (110) facet (93.34%) is much higher than that of Cu/CeO2-nanocubes (Cu/CeO2-C) with the (100) facet (32.22%) and Cu/CeO2-nanooctahedra (Cu/CeO2-O) with the (111) facet (15.20%). DFT calculation shows that Cu 3d exhibits orbital hybridization with Ce 5d and 4f, which provides a favorable pathway for electron transfer. This work delves into the facet-performance relationship during the photocatalytic process.