With the development of the global economy, large amounts of fossil fuels are being burned, causing a severe energy crisis and climate change. Photocatalytic CO₂ reduction is a clean and environmentally friendly method to convert CO₂ into hydrocarbon fuel, providing a feasible solution to the global energy crisis and climate problems. Photocatalytic CO₂ reduction has three key steps: solar energy absorption, electron transfer, and CO₂ catalytic reduction. The previous literature has obtained many significant results around the first two steps, while in the third step, there are few results due to the need to add a co-catalyst. In general, the co-catalysts have three essential roles: (1) promoting the separation of photoexcited electron–hole pairs, (2) inhibiting side reactions, and (3) improving the selectivity of target products. This paper summarizes different types of photocatalysts for photocatalytic CO₂ reduction, the reaction mechanisms are illustrated, and the application prospects are prospected.

Urgent and significant, the mitigation of greenhouse effects and the preservation of the Earth's ecological environment are paramount concerns. Photocatalytic carbon dioxide (CO₂) reduction technology holds immense promise as it directly harnesses renewable solar energy to convert CO₂ into hydrocarbon fuels and valuable chemical products. Indium (In)-based sulfides have garnered significant attention in the realm of fundamental research on CO₂ photocatalytic conversion. The photocatalytic performance exhibited by In-based materials is attributed to the appropriate bandgap (E _g), unique electronic states, tunable atomic structure, and superior optoelectronic properties. Notably, In-based metal sulfides also show excellent potential for addressing challenges related to photocorrosion and carrier recombination. This paper highlighted the key structural features and commonly employed synthesis techniques of In-based metal sulfides. Furthermore, it summarized effective modification strategies aimed at optimizing the photocatalytic performance of these materials. A particular focus was placed on exploring the intricate structure-activity relationships, encompassing the influence of heterostructure construction, element doping, defect engineering, and co-catalyst modification on enhancing photocatalytic efficiency. Finally, the article identified the current challenges and outlined the promising future directions for In-based photocatalysts, hoping to provide valuable references for researchers.

Cu ₂ O nanoparticles and MoS ₂ nanoflowers decorated with ZnO nanospheres were successfully co-deposited on Cu mesh via a mild electrodeposition method to build a dual direct Z-scheme heterostructure. The prepared materials can effectively synthesize ammonia with N ₂ and H ₂ O in the liquid membrane reactor under simulated visible light. The results indicate that 3D nanomaterials exhibit better performance compared to a pure semiconductor due to the synergistic effect of enhanced visible light absorption, longer photogenerated carrier lifetime and the specific charge transfer path of dual direct Z-scheme structure. Meanwhile, the hydrophilicity of Cu ₂ O/MoS ₂ /ZnO rapidly makes the surface of the catalyst wet when it participates in the photo reaction, which promotes the contact between the reactant and exciton. This work proposes the electron transfer and possible reaction mechanism corresponding to the designed catalyst, which can provide a reference for other photocatalytic applications using a semiconductor heterojunction as a catalyst.