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

ZnIn 2 S 4 /ZnO heterostructures have been synthesized by a simple one-step hydrothermal synthesis method, which lead to ZnO grow on the surface of ZnIn 2 S 4 nanosheets, forming a strong electronic interaction between the two semiconductors. Under the full spectrum irradiation, the optimal photocatalyst 2ZnIn 2 S 4 /ZnO shows the H 2 evolution rate of 13,638 (water/ethanol = 1:1) and 3036 (water) μmol•g−1h−1, which is correspondingly 4 and 5 times higher than that of pure ZnIn 2 S 4. ISI-XPS analysis and DFT calculations show that electrons are transferred from ZnIn 2 S 4 to ZnO through hybridization and an internal electric field (IEF) is formed between ZnIn 2 S 4 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 ZnIn 2 S 4 /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. [Display omitted] ZnIn 2 S 4 /ZnO heterostructures have been achieved by a simple in-situ growth solvothermal method. Under full spectrum irradiation, the optimal photocatalyst 2ZnIn 2 S 4 /ZnO exhibits H 2 evolution rate of 13,638 (water/ethanol = 1:1) and 3036 (water) μmol·g−1h−1, which is respectively 4 and 5 times higher than that of pure ZnIn 2 S 4. In situ illumination X-ray photoelectron spectroscopy (ISI-XPS) analysis and density functional theory (DFT) calculations show that the electrons of ZnIn 2 S 4 are removed to ZnO through hybridization and form an internal electric field between ZnIn 2 S 4 and ZnO. The optical properties of the catalyst and the effect of internal electric field (IEF) can increase photo-generated electrons (e−)–holes (h+) transport rate and enhance light collection, resulting in profitable photocatalytic properties. The photoelectrochemical and EPR results show that a stepped (S-scheme) heterojunction is formed in the ZnIn 2 S 4 /ZnO redox center, which greatly promotes separation of e−–h+ pairs and efficient H 2 evolution. This research offers an effective method for constructing an efficient S-Scheme photocatalytic system for H 2 evolution. [ABSTRACT FROM AUTHOR]