Strong interaction between sulfur sites and oxygen vacancies in Z-scheme ZnIn2S4/TiO2-x heterojunction for improved photocatalytic hydrogen yield and stability

It is always interesting but challenge to reasonably design efficient and stable hierarchical photocatalyst for H2 evolution from water. In this paper, we synthesized ZnIn2S4/TiO2-x (ZIS/TiVo) heterojunction by adjusting the ratio of ZIS to TiVo and Vo concentration. Importantly, the results from various characterizations such as HRTEM, STEM/EDS, XPS, EPR, and Raman proved the existence of strong interaction between sulfur sites and Ti3+/Vo by charge attraction. Such interaction along the interface of heterojunction generated the synergy, which extended light response to visible-infrared range, significantly facilitated charge separation and transfer through Z-scheme, stabilized S and Vo sites without sacrifice during reaction, but also provided active sites for water activation. As result, the optimal 30ZIS/TiVo-B showed over 20 and 4 times higher H2 production activity than TiO2 and ZnIn2S4, respectively. 30ZIS/TiVo-B also demonstrated excellent long-term stability without deactivation, while the activity of 30ZIS/TiO2 decreased by 90 % after 56 h. Findings from this work can open a new avenue to design photocatalyst with high activity and stability by controlling active sites and their interaction.