Abstract:Under the guidance of China's "peak carbon dioxide emissions" and "carbon neutrality" targets, research on carbon dioxide (CO2) conversion into high-value carbon-containing products is of significant importance. However, most photocatalysts suffer from the low separation efficiency of photogenerated charge carriers and a scarcity of reaction sites, leading to a low photocatalytic CO2 reduction activity. Copper (Cu) attracts widespread attention in the field of photocatalytic CO2 reduction due to the non-toxicity, abundant reserves, and excellent catalytic performance. In addition to low cost and ease to prepare, Cu-based photocatalysts possess many characteristics such as tunable electronic structures, excellent CO2 adsorption properties, and stable reaction intermediates that promote C-C coupling, which are conducive to the formation of C2+ products in the reaction. Cu as the catalytic sites can effectively improve the photocatalytic CO2 reduction. By regulating the electronic structure of Cu catalytic sites, the selectivity of photocatalytic CO2 reduction can be enhanced. On the other hand, abundant catalytic sites act as channels for the transfer of photogenerated electrons, accelerating the separation of photogenerated charge carriers in the semiconductor photocatalyst. Based on different design schemes, this article discussed the impact of three different forms of Cu catalytic sites on photocatalytic CO2 reduction and provided an outlook on the future development of Cu catalytic site design in the field of photocatalytic CO2 reduction.