A novel Co3O4/ZnSe S-scheme heterojunction photocatalyst with efficient carrier separation and enhanced light absorption for photocatalytic hydrogen evolution

Designing the heterojunction is an efficient method to boost the H2 evolution activity of photocatalysts. Here, to enhance the photocatalytic activity of ZnSe, ZnSe particles were attached to the flower-like Co3O4 surface to form S-scheme heterojunctions. Under visible light exposure, the H2 production rate of the 3wt%Co3O4/ZnSe (COZS) composite was 4197.36 μmol g-1 h-1, which was approximately 5.5 and 18.2 times that of 1%Pt-ZnSe (756.76 μmol g-1 h-1) and ZnSe (230.52 μmol g-1 h-1). X-ray photoelectron spectroscopy (XPS), electrochemical and photoluminescence results revealed that the recombination of carriers was effectively inhibited, which may be attributed to Co3+/Co2+ autooxidation-reduction pairs and S-scheme heterojunction. According to the specific surface area results, Co3O4 was beneficial in increasing the specific surface area of composite photocatalyst and exposing more active sites, thereby improving photocatalytic activity. Moreover, the optical test results displayed that the light absorbing range of COZS was broadened to the entire visible spectrum, which may promote the increase of photogenerated carriers. According to the band structure of COZS and the possible path of electron transfer, the photocatalytic mechanism was discussed.