Cr dopants and S vacancies in ZnS to trigger efficient photocatalytic H2 evolution and CO2 reduction

Abstract

Driven by endless solar energy, photocatalytic H2 evolution from water splitting and CO2 conversion to hydrocarbon fuels over semiconductor photocatalysts are of great potential to simultaneously settle the greenhouse effect and energy shortage. Herein, Cr-doped zinc sulfide (ZnS) with accompanying sulphur vacancies (Vs) photocatalytic materials is developed by a facile hydrothermal method. The Cr dopants centralize photoinduced holes and Vs trap electrons, forming a synergistic effect for accelerating charge separation and transfer. The reaction energy barrier for both H2 evolution and CO2 reduction has been optimized. Therefore, in the absence of a cocatalyst, the optimal catalyst (Zn0.94Cr0.06S) achieves an outstanding H2 evolution activity of 20.3 mmol g−1 h−1, which is approximately 2.9 times higher than 6.9 mmol g−1 h−1 for pristine ZnS. In addition, in the gas-solid reaction system without co-catalysts or sacrificial agents, the Zn0.94Cr0.06S exhibits a considerable CO evolution rate of 19.56 μmol g−1 h−1, about 10.1 times higher than ZnS (1.94 μmol g−1 h−1). Both the performances for H2 evolution and CO2 reduction of Zn0.94Cr0.06S outperform most of the previously reported photocatalysts. Particularly, the Zn0.94Cr0.06S possesses superior stability, the photoactivity of which exhibits no noticeable deactivation after six cycles’ reactions. This work may shed light on the rational design and fabrication of highly efficient materials via combining individual element doping and defect engineering.