Construction of defective ZnIn2S4 and immobilized TiO2 heterostructures: Synergistic regulation of ZnIn2S4/TiO2/MS-SiO2 composite photocatalyst performance

Defect engineering and heterojunction are the two dominant methods to improve the efficiency of semiconductor photocatalysis. Loading can also improve the performance of photocatalysts and solve the problems of photocatalyst agglomeration and difficult recovery in water. In this paper, a ternary ZnIn2S4/TiO2/MS-SiO2 composite photocatalyst (EG-ZIS/TS) was constructed by sequentially loading nano-TiO2 and defective state ZnIn2S4 (EG-ZIS) on industrial by-product SiO2 microspheres (MS-SiO2). Among them, EG-ZIS was prepared with ethylene glycol as a solvent. Compared with EG-ZIS/T (unloaded MS-SiO2) and ZIS/TS (non-defected state ZnIn2S4), the degradation performance of methyl orange (MO) solution and the reduction performance of hexavalent chromium under simulated daylight irradiation were substantially improved. As a result, Zn defects enhanced the photocatalytic performance of ZnIn2S4 and the heterojunction between ZnIn2S4 and TiO2, and this enhancement was achieved by adjusting the work function of the system and promoting interface electronic transmission. The loading of MS-SiO2 further produced a synergistic effect of enhancing the heterojunction photocatalytic efficiency by improving the dispersion and immobilization of TiO2 and EG-ZIS. The effect of ethylene glycol on the curvature and surface Zn defectivity of ZnIn2S4 nanosheets was also investigated in this study. This study provides an innovative approach to improve the oxidation and reduction performance of photocatalysts by combining semiconductor defect, heterojunction, and loading on the carrier surface and finds that the loading of photocatalysts on the SiO2 carrier surface has an enhancement effect on the performance of the formed heterojunction. This thesis is useful and informative for related research.