Photocatalytic H2 production over CoxNi0.85-xSe decorated TiO2 S-scheme heterojunction

Abstract

The construction of an S-scheme heterojunction facilitates the efficient separation of charges and preserves its high REDOX potential. In this study, a series of CoxNi0.85-xSe(x=0.05,0.1,0.2,0.3and0.4) and TiO2 nanoparticles were both prepared using solvothermal method, and then Co0.3Ni0.55Se was combined with TiO2 to form Co0.3Ni0.55Se/TiO2 heterojunction through a solvent evaporation strategy for efficient photocatalytic H2 production. It found that the H2 production rate of 10 wt%-Co0.3Ni0.55Se/TiO2 composite can reach 10,070.9 µmol∙g−1∙h−1 with TEOA as a sacrificial agent under a simulated sunlight irradiation, which is 307.9, 33.5and 3.3 times higher than those of pure Co0.3Ni0.55Se,TiO2 and 10 wt%-Ni0.85Se/TiO2, respectively. This enhanced performance is primarily attributed to the formation of an S-scheme heterojunction between TiO2 and Co0.3Ni0.55Se, which effectively enhances light absorption capacity and facilitates charge separation and migration during light irradiation processes. Especially, the S-scheme charge separation can retain the active REDOX capacity of electrons in the conduction band of CoxNi0.85-xSe and the holes in the valance band of TiO2, thereby promoting H2 generation. This study demonstrates that CoxNi0.85-xSe serves as a reducing photocatalyst that offers a viable approach for achieving ideal S-scheme heterojunctions.