In situ XPS proved efficient charge transfer and ion adsorption of ZnCo2O4/CoS S-Scheme heterojunctions for photocatalytic hydrogen evolution

Enhancing photogenerated charge transfer is an effective way of enhancing photocatalytic hydrogen production activity. The good electrical conductivity of ZnCo2O4 enhances the charge transfer rate, while CoS as the active site ensures the thermodynamic conditions for the hydrogen production reaction. The composite of p-type ZnCo2O4 and n-type CoS has a strong surface interaction, and the more negative surface potential of composite catalyst provides favourable conditions for its H+ adsorption. The intrinsic charge transfer mechanism and the reasons for the enhanced photocatalytic activity were analyzed by photoelectrochemical characterisations. The construction of S-Scheme heterojunction effectively accelerates the charge transfer rate between catalysts and is the main reason for the enhanced photocatalytic hydrogen evolution performance. More importantly, the charge transfer mechanism of S-Scheme heterojunction was strongly demonstrated by in situ XPS. This work provides an approach to the development of S-Scheme heterojunctions in the field of photocatalysis.