Efficient photocatalytic hydrogen production by space separation of photo-generated charges from S-scheme ZnIn2S4/ZnO heterojunction

ZnIn2S4/ZnO heterostructures have been synthesized by a simple one-step hydrothermal synthesis method, which lead to ZnO grow on the surface of ZnIn2S4 nanosheets, forming a strong electronic interaction between the two semiconductors. Under the full spectrum irradiation, the optimal photocatalyst 2ZnIn2S4/ZnO shows the H2 evolution rate of 13,638 (water/ethanol = 1:1) and 3036 (water) & mu;mol & BULL;g � 1h- 1, which is correspondingly 4 and 5 times higher than that of pure ZnIn2S4. ISI-XPS analysis and DFT calculations show that electrons are transferred from ZnIn2S4 to ZnO through hybridization and an internal electric field (IEF) is formed between ZnIn2S4 and ZnO. The improvement of photocatalytic performance can be attributed to the effect of internal electric field, the increase of photo generated electron and hole transport rate, the suppression of charge carrier recombination, and the enhancement of light collection. The photoelectrochemical and EPR results show that a stepped (S-scheme) heterojunction is formed in the ZnIn2S4/ZnO redox center, which greatly promotes separation of electron-hole pairs to promote efficient hydrogen evolution. This work provides a new strategy for the design of S-scheme photocatalytic systems for hydrogen evolution.