Rationally designed ternary CdSe/WS2/g-C3N4 hybrid photocatalysts with significantly enhanced hydrogen evolution activity and mechanism insight

Excellent light harvest, efficient charge separation and sufficiently exposed surface active sites are crucial for a given photocatalyst to obtain excellent photocatalytic performances. The construction of two-dimensional/two-dimensional (2D/2D) or zero-dimensional/2D (0D/2D) binary heterojunctions is one of the effective ways to address these crucial issues. Herein, a ternary CdSe/WS2/g-C3N4 composite photocatalyst through decorating WS2/g-C3N4 2D/2D nanosheets (NSs) with CdSe quantum dots (QDs) was developed to further increase the light harvest and accelerate the separation and migration of photogenerated electron-hole pairs and thus enhance the solar to hydrogen conversion efficiency. As expected, a remarkably enhanced photocatalytic hydrogen evolution rate of 1.29 mmol g(-1) h(-1) was obtained for such a specially designed CdSe/WS2/g-C3N4 composite photocatalyst, which was about 3.0, 1.7 and 1.3 times greater than those of the pristine g-C3N4 NSs (0.43 mmol g(-1) h(-1)), WS2/g-C3N4 2D/2D NSs (0.74 mmol g(-1) h(-1)) and CdSe/g-C3N4 0D/2D composites (0.96 mmol g(-1) h(-1)), respectively. The superior photocatalytic performance of the prepared ternary CdSe/WS2/g-C3N4 composite could be mainly attributed to the effective charge separation and migration as well as the suppressed photogenerated charge recombination induced by the constructed type-II/type-II heterojunction at the interfaces between g-C3N4 NSs, CdSe QDs and WS2 NSs. Thus, the developed 0D/2D/2D ternary type-II/type-II heterojunction in this work opens up a new insight in designing novel heterogeneous photocatalysts for highly efficient photocatalytic hydrogen evolution. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, a ternary CdSe/WS2/g-C3N4 composite photocatalyst was developed by decorating nanosheets with quantum dots and constructing 2D/2D heterojunctions, leading to enhanced light harvest, accelerated charge separation, and improved efficiency in solar to hydrogen conversion. The superior photocatalytic performance was mainly attributed to effective charge separation and migration, as well as suppressed charge recombination induced by the constructed type-II heterojunctions at the interfaces.