Porous Coral-like Z-Scheme g-C3N4/ZnIn2S4 Heterojunction Xerogel for Promoting CO2 Photoreduction Activity

Designing a photocatalyst with high mass transfer efficiency and catalytic activity is a key step in CO₂ capture, utilization, and storage (CCUS) technology systems. Aerogel (or xerogel) materials are regarded as one of the best morphologies for the construction of catalysts because of their unique porous structures. In this work, ZnIn₂S₄ nanosheets were grown on 2D g-C₃N₄ nanoplates by the solvothermal method and formed into xerogel by freeze-drying with a unique coral-like porous structure. The as-prepared composite photocatalyst with a 1:1 mass ratio of g-C₃N₄ and ZnIn₂S₄ demonstrated an impressive CO yield of 2.66 μmol g^–1 h^–1 and the CH₄ production rate was 1.91 μmol g^–1 h^–1, which were increased by 11.08 times and 10.61 times higher than single ZnIn₂S₄. A series of characterizations and DFT calculations revealed the reaction mechanism. This unique porous morphology provides abundant active reaction sites, improves the efficiency of light absorption and utilization, and improves the mass transfer performance. Furthermore, the formation of Z-scheme heterojunctions between the two precursors enhances the production efficiency and transmission performance of photogenerated carriers. This work contributes a new direction in the design of catalyst morphology and offers more insight into the field of CO₂ photoreduction.