Construction of 3D/2D CeO ₂ /Bi ₂ MoO ₆ S‐scheme heterojunction for photocatalytic cascade reactions of secondary amines synthesis

Abstract Rare‐earth metal oxide CeO 2 with a unique electronic structure has always been one of the popular research materials in the field of catalysis. However, due to its inherent band structure limitations and the recombination of photo‐generated carriers, its photocatalytic performance still needs to be rationally optimized and improved. Here, an in situ assembly method was employed to construct 3D/2D CeO 2 /Bi 2 MoO 6 (Ce/BMO) S‐scheme heterojunctions for enhanced tandem reaction of photocatalytic secondary amines synthesis. Experimental results and density functional theory calculations reveal that the transfer of photo‐generated carriers between CeO 2 and Bi 2 MoO 6 (BMO) conforms to the S‐scheme heterojunction mechanism which regulates the band structure and greatly promotes the separation and effective utilization of photo‐generated carriers. In situ Fourier‐transform infrared (in situ FTIR) spectra and adsorption energy calculations demonstrate that the unique Ce 3+ /Ce 4+ component in CeO 2 promotes the nitrobenzene adsorption and the unsaturated Mo sites on Bi 2 MoO 6 are responsible for benzyl alcohol adsorption, which is highly favorable for surface oxidation and reduction reactions. Thus, the optimal 0.7‐CeO 2 /Bi 2 MoO 6 (0.7Ce/BMO) exhibited a 93% conversion rate of nitrobenzene and a 91% selectivity for secondary amines. This work emphasizes the crucial role of S‐scheme heterojunctions for constructing efficient rare‐earth metal oxide‐based composite photocatalysts.