Construction of a sunflower-like S-scheme WO3/ZnIn2S4 heterojunction with spatial charge transfer for enhanced photocatalytic CO2 reduction

The construction of step-scheme (S-scheme) heterojunction has become an effective strategy for enhancing photocatalytic CO2 reduction. In this study, a sunflower-like S-scheme WO3/ZnIn2S4 heterostructure is fabricated through the in-situ growth of ZnIn2S4 nanosheets on WO3 hollow sphere, aimed at improving selective CO2 reduction. The constructed embedding configuration, featuring a WO3 hollow sphere core and an outer layer of ZnIn2S4 nanosheet, increases the contact interface and establishes a significant built-in electric field, thereby promoting the migration and separation of photogenerated carriers. The confined internal cavity of the threedimensional (3D) sunflower-like architecture aids in limiting the free diffusion of CO2, and enriching CO2 molecules at the surface of the photocatalyst, consequently enhancing reaction kinetics. Moreover, S vacancies on ZnIn2S4 nanosheets promote the chemisorption and activation of CO2. As a result, the optimized evolution rates for CH4 and CO of 58.7 mu mol g-1h- 1 and 51.3 mu mol g-1h- 1, respectively, are achieved for WO3/ZnIn2S4 heterojunction. The corresponding electron selectivity for CH4 reaches 82.1 %, which is 13 and 1.5 times higher than those of bare WO3 and ZnIn2S4, respectively. This provides valuable insights into the design of muti-functionalized S-scheme heterojunction photocatalysts.