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.