Constructing an S-scheme heterojunction of 2D/2D Cd0.5Zn0.5S/CuInS2 nanosheet with vacancies for photocatalytic hydrogen generation under visible light

Abstract

Exploring efficient and stable water-splitting photocatalysts is critical for realizing conversion solar energy into hydrogen energy. Herein, a unique 2D/2D S-scheme Cd0.5Zn0.5S/CuInS2 heterojunction with sulfur vacancies was rationally designed by chemically converting inorganic–organic hybrid ZnS(en)0.5 into inorganic Cd0.5Zn0.5S nanosheets and fabricating with CuInS2 at 350 °C under an N2 atmosphere. The final Cd0.5Zn0.5S/CuInS2 photocatalyst was composed of thin nanosheets with a substantial interfacial contact area, which enhanced light absorption and allowed directional charge transfer and separation. Under visible light irradiation, the photocatalytic H2 evolution activities of Cd0.5Zn0.5S nanosheets is 0.79 mmol·g−1·h−1, which is greater than other solid solution materials obtained by varying Cd and Zn ratios. The 2D/2D nanosheets with 8% CuInS2 exhibit excellent hydrogen evolution activity with yields of 7.73 mmol·g−1·h−1, which are 9.8 and 138 times higher than Cd0.5Zn0.5S and CuInS2. In addition, Cd0.5Zn0.5S/CuInS2 photocatalyst demonstrates outstanding stability and activity over the course of 24-hour period. Moreover, the transfer pathway of photogenerated charges were explored by the energy band bending, which proved that an S-scheme heterojunction is synthesized successfully.This work offers a useful methodology for analyzing S-scheme heterojunction with abundant sulfur vacancies, and improving the solar hydrogen evolution performance of Cd0.5Zn0.5S photocatalyst.