Hollow spherical biomass derived-carbon dotted with SnS2/g-C3N4 Z-scheme heterojunction for efficient CO2 photoreduction into CO

Abstract

The core of realizing the effective CO2 conversion by solar energy is to develop a stable photocatalyst with high CO2 adsorption capacity and high charge separation efficiency. In this work, a hollow spherical Z-scheme SnS2/g-C3N4/C (SCC) photocatalyst is successfully constructed by a morphology-inherited strategy. Biomass mabospores are utilized as both the precursor for formation of hollow spherical structure and carbon source, and the g-C3N4 and SnS2 nanosheets tightly anchor on the surface of mabospores-derived carbon spheres. The Z-scheme SCC heterostructure exhibits 5.5 times activity enhancement on CO2 photoreduction to CO with a high evolution rate up to 40.86 μmol∙g−1∙h−1. Examined by various photoelectrochemical analysis, the boosted photocatalytic activity originates mainly from the construction of hollow spherical Z-scheme heterojunction, providing the more preferable basic sites for CO2 adsorption, promoting the separation efficiency of electron-hole pairs, as well as increasing the reductionability of electrons in conduction band of g-C3N4. The formed internal electric fields between the g-C3N4 and SnS2 can also further reinforce the spatial separation of photogenerated charge carriers. Theoretical calculations further verify that the SCC Z-scheme heterostructure can effectively decrease the energy barriers of formed intermediates, especially the crucial COOH*, and thus leading to the facile conversion of CO2-to-CO. This work induces a new strategy to construct g-C3N4-based Z-scheme heterojunction assisted by versatile biomasses with optimized structure and enhanced photoelectrochemical merits for efficient CO2 conversion into chemical fuels.