Over efficient photocatalysts, CO
2 photoreduction typically converts CO
2 into low-carbon chemicals, which serve as raw materials for downstream synthesis processes. Here, an efficient composite photocatalyst heterojunction (Cu
2O-u/g-C
3N
4) has been fabricated to reduce CO
2.
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Over efficient photocatalysts, CO
2 photoreduction typically converts CO
2 into low-carbon chemicals, which serve as raw materials for downstream synthesis processes. Here, an efficient composite photocatalyst heterojunction (Cu
2O-u/g-C
3N
4) has been fabricated to reduce CO
2. Graphitic carbon nitride (g-C
3N
4) was synthesized via thermal polymerization of urea at 550 °C, while pre-dispersed Cu
2O derived from urea pyrolysis (Cu
2O-u) was prepared by thermal reduction of urea and CuCl
2·2H
2O at 180 °C. The heterojunction Cu
2O-u/g-C
3N
4 was subsequently constructed through hydrothermal treatment at 180 °C. This heterojunction exhibited a bandgap of 2.10 eV, with dual optical absorption edges at 485 nm and above 800 nm, enabling efficient harvesting of solar light. Under 175 W mercury lamp irradiation, the heterojunction catalyzed liquid-phase CO
2 photoreduction to formic acid, acetic acid, and methanol. Its formic acid production activity surpassed that of pristine g-C
3N
4 by 3.14-fold and TiO
2 by 8.72-fold. Reaction media, hole scavengers, and reaction duration modulated product selectivity. In acetonitrile/isopropanol systems, formic acid and acetic acid production reached 579.4 and 582.8 μmol·h
−1·g
cat−1. Conversely, in water/triethanolamine systems, methanol production reached 3061.6 μmol·h
−1·g
cat−1, with 94.79% of the initial conversion retained after three cycles. Finally, this work ends with the conclusions of the CO
2 photocatalytic reduction to formic acid, acetic acid, and methanol, and recommends prospects for future research.
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