Considering the high energy demand in modern society and the widespread acceptance of "carbon neutrality" policies, reducing CO 2 into value-added products through "artificial carbon cycling" seems more reasonable and attractive. [3,4] Among the various methods of CO 2 resource utilization, photocatalysis (PC), electrocatalysis (EC) and photoelectrocatalysis (PEC), which can be operated at room temperature and atmospheric pressure, are considered to be a relatively feasible scheme. [5][6][7][8][9] Photocatalysis based on semiconductor materials can directly absorb solar light and generate charge carriers with redox capability, simultaneously accomplishing energy storage and carbon reduction. [10][11][12][13] Electrocatalysis can be driven by multiple forms of renewable energy (solar energy, water energy, wind energy, biomass energy, wave energy, tidal energy, etc.) to realize the conversion of CO 2 at the suitable negative potential. [14][15][16] Photo electrocatalysis is a special combination of photocatalysis and electrocatalysis, using a semiconductor electrode with light response capability to achieve efficient CO 2 reduction. [17,18] However, CO 2 exhibits chemical inertness due to its linear molecular and high CO bond energy, which is owing to the adoption of sp hybrid orbital when C atoms bond with O atoms. [19][20][21] Therefore, it is challenging to activate CO 2 and convert it into desirable products thermodynamically. [22] In addition, the CO 2 reduction reaction involves multi-step electron transfer, hydrogenation and CC bond coupling, which determines it has a complex and stochastic reaction path. Therefore, developing an ideal catalyst with high activity, stability, and economy for CO 2 reduction is necessary.Since Inoue et al. successfully converted CO 2 into formic acid, formaldehyde, methanol and methane under sunlight irradiation, many semiconductor materials for CO 2 reduction have been developed and evaluated. [23][24][25][26] The n-type semiconductors, including TiO 2 , ZnO 2 and SrTiO 3 , have attracted wide attention due to their low cost, high photostability and environmental harmlessness. [27] However, the excessive band gap limits their light response range, making them unsuitable for the CO 2 conversion systems driven by solar light. [28,29] Cuprous oxide (Cu 2 O), as one of the copper-based semiconductors with abundant reserves on the earth, has a suitable band gap to absorb visible light, which occupies 42-43% of the solar spectrum. More Converting CO 2 into value-added products by photocatalysis, electrocatalysis, and photoelectrocatalysis is a promising method to alleviate the global environmental problems and energy crisis. Among the semiconductor materials applied in CO 2 catalytic reduction, Cu 2 O has the advantages of abundant reserves, low price and environmental friendliness. Moreover, Cu 2 O has unique adsorption and activation properties for CO 2 , which is conducive to the generation of C 2+ products through CC coupling. This review introduces the basic principles of CO...