The steadily growing overconsumption of fossil fuels and the associated massive CO emissions2 caused a serious energy crisis and environmental problems. Photoelectrochemical (PEC) reduction of CO2 that can combine and optimize the benefits of photocatalysis and electrocatalysis was seen as an attractive prospect for solving both problems. Here, photocathode materials are the cores of PEC CO2 reduction. Among various photocathodes, Cu-based photocathodes are popular due to their low toxicity, low cost, earth-rich properties, suitable band gap values and favorable band edges for CO. a lot of attention to2 reduction. More specifically, Cu-based photocathodes have unique advantages for hydrocarbon production such as CO, HCOOH, CH4th or, more importantly, C2 Products (such as C2H4th, C2H5OH and C2H6th) compared to other metal-based photoelectrodes. An insight into the relationships between the properties and functions of photocathodes is provided in the PEC CO area. a crucial role2 reduction. This Review presents the development of Cu-based photocathode materials and discusses future research directions. The photocathode systems mainly comprise Cu-based oxides, Cu-based chalcogenides and Cu-based electrocatalyst-coupled photocathodes. Then the existing main advantages and disadvantages of each system are discussed. In summary, by combining our analyzes of the reported photocathodes, we will offer future challenges for the rational design of photoelectrodes. Overall, this Review will provide an important overview of Cu-based photocathodes for PEC reduction of CO. give2.