3.8 Photocatalytic H2 evolution mechanism
Based on the above experimental results, the H2evolution mechanism of the hierarchical CoP/ZnCdS/Co3O4 QDs bi-heterostructure cages as a photocatalyst exhibiting ultrahigh hydrogen evolution activity is depicted as shown in Fig. 9. Under visible light irradiation, ZnCdS solid solution being inherently active to splitting of water is excited to generate electrons and holes, and the produced charges are rapidly captured and transferred by the excellent-performance CoP and Co3O4 QDs while the holes on valence band of ZnCdS react with LA as the sacrificial reagent, which lead to that the recombination of electron-hole pairs is greatly inhibited, thereby the high-performance photocatalytic hydrogen evolution come. In short, the construction of the bi-heterostructured cages in CoP/ZnCdS/Co3O4 QDs develops the two parallel pathways applied to the rapid electron transport, resulting in the serious improvement of the utilization efficiency of photo-induced charges on conduction band of ZnCdS for hydrogen evolution.