Construction of CuInS2/C/TiO2 hierarchical tandem heterostructures with optimized CO2 photoreduction under visible light

The precise regulation of the nano-catalyst structure is a big challenge that limits the application of photocatalytic technology in CO2 reduction. Herein, to improve the utilization of sunlight, the separation and transfer efficiency of photogenerated electron-hole pairs, and the surface catalytic reaction process, CuInS2/C/TiO2 (CIS/C/T) hierarchical tandem heterostructure have been rationally designed. Multiple in-situ characterizations and DFT simulations show that CQDs not only act as a co-catalyst, but also act as a bridge between TiO2 (T) and CuInS2 (CIS), which further attribute to the efficient separation and enrichment of photogenerated electron-hole pairs while effectively avoiding the recombination. In consideration of the excellent broad-spectrum absorption, the CO2-to-CO photoreduction performance of the optimal CIS/C/T reaches up to 7.73 μmol g-1h−1, about 3.16 times enhancement of C/T. Combined with in-situ DRIFTs, the intrinsic structure–activity relationship is pointed out, and extended to other similar TiO2-based catalytic systems (In2S3/C/TiO2). This work will provide a new universal strategy for the design and synthesis of high-performance nano-photocatalysts.