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

Abstract

• Constructed CuInS 2 /C/TiO 2 hierarchical tandem heterostructures with flame process. • Synergistic characterization of material structure by multiple in-situ methods. • Enhanced the CO 2 -to-CO performance by 3.16 times of the C/T under visible light. • Revealed the relationship between the behavior of electrons and the photocatalytic mechanism. • Promoted to the other TiO 2 -based system as a universal strategy. The precise regulation of the nano-catalyst structure is a big challenge that limits the application of photocatalytic technology in CO 2 reduction. Herein, to improve the utilization of sunlight, the separation and transfer efficiency of photogenerated electron-hole pairs, and the surface catalytic reaction process, CuInS 2 /C/TiO 2 (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 TiO 2 (T) and CuInS 2 (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 CO 2 -to-CO photoreduction performance of the optimal CIS/C/T reaches up to 7.73 μmol g -1 h −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 TiO 2 -based catalytic systems (In 2 S 3 /C/TiO 2 ). This work will provide a new universal strategy for the design and synthesis of high-performance nano-photocatalysts.