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Vs-WS2; ZnCdS; S vacancy; Photocatalytic hydrogen evolution; S-scheme heterojunction
ABSTRACT
The rational construction of active sites on the inner surface of heterojunction can enhance the photocatalyst carrier separation efficiency and photocatalytic activity. Herein, the sulfur-deficient-rich WS2 (Vs-WS2) was selected and complexed with ZnCdS to construct a step-scheme (S-scheme) heterojunction (ZCSW-Vs) with good photocatalytic hydrogen evolution reaction (HER) activity. The optimized photocatalyst ZCSW-Vs exhibited excellent H2 evolution rate of 84.63 mmol g-1 h-1, which was about 14-fold enhanced compared with that of ZCSW. The excellent photocatalytic activity was attributed to S vacancies optimizing the adsorption of hydrogen during the reaction process, according to characterization and density functional theory (DFT) calculations. In addition, the internal electric field of the ZCSW-Vs heterojunction significantly promoted carrier-directed migration. This work provides the insights into the design of efficient photocatalytic materials and the explanation of the reaction mechanism through the synergistic effect of vacancies and S-scheme heterojunctions.