In-situ synthesized oxygen vacancy filled ZnS/Vo-ZnO heterojunction photocatalysts for efficient H2 production

Defect-filled ZnO-based heterojunctions have gained attention in photocatalytic hydrogen (H2) production due to their ability to reduce the recombination rate of photogenerated carriers at the heterojunction interface. In this study, the surface oxygen vacancy defects on ZnO (Vo-ZnO) were precisely tailored by decomposing the deep eutectic solvents (DES) prepared ZnO/Zn(OH)2 complex. The defective surfaces of Vo-ZnO act as nucleation sites for binding S atoms on their oxygen vacancies during in-situ photodeposition, resulting in the formation of ZnS. In this process, oxygen vacancies on the surface are electronically filled, and ZnS is simultaneously grown on ZnO. As a result, the ZnS/Vo-ZnO heterojunction photocatalyst exhibits a higher donor charge density (ND) of 3.80 × 1021 cm−3 and reduces the charge transfer resistance (Rct) by 22 kΩ compared to Vo-ZnO. The ZnS/Vo-ZnO has an H2 production rate of 18.84 mmol g−1 h−1 and follows the type-II heterojunction for charge separation. The prolonged photoluminescence lifetime (τave = 1.6 ns) in the ZnS/Vo-ZnO is attributed to the heterojunction interface between ZnS and defective ZnO. The proposed approach creates a new synthesis route for constructing the type-II heterojunction between ZnS and Vo-ZnO via an in-situ photodeposition process.