Vacancy engineering mediated hollow structured ZnO/ZnS S-scheme heterojunction for highly efficient photocatalytic H2 production

Designing a step-scheme (S-scheme) heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H₂ production activity. Herein, a hollow ZnO/ZnS S-scheme heterojunction with O and Zn vacancies (V_{O, Zn}-ZnO/ZnS) is rationally constructed via ion-exchange and calcination treatments. In such a photocatalytic system, the hollow structure combined with the introduction of dual vacancies endows the adequate light absorption. Moreover, the O and Zn vacancies serve as the trapping sites for photo-induced electrons and holes, respectively, which are beneficial for promoting the photo-induced carrier separation. Meanwhile, the S-scheme charge transfer mechanism can not only improve the separation and transfer efficiencies of photo-induced carrier but also retain the strong redox capacity. As expected, the optimized V_{O, Zn}-ZnO/ZnS heterojunction exhibits a superior photocatalytic H₂ production rate of 160.91 mmol g^–1 h^–1, approximately 643.6 times and 214.5 times with respect to that obtained on pure ZnO and ZnS, respectively. Simultaneously, the experimental results and density functional theory calculations disclose that the photo-induced carrier transfer pathway follows the S‐scheme heterojunction mechanism and the introduction of O and Zn vacancies reduces the surface reaction barrier. This work provides an innovative strategy of vacancy engineering in S-scheme heterojunction for solar‐to‐fuel energy conversion.