Photocatalytic CO2 Reduction with 100% CO Selectivity Using In2O3/CuO/g-C3N4 Ternary Composites

The key challenge in photocatalytic CO2 reduction is to develop photocatalysts with high performance and ultrastability. Graphitic carbon nitride (g-C3N4) is a promising semiconductor photocatalyst due to its low cost, simple preparation, and stability. However, bulk g-C3N4 exhibits limitations such as low specific surface area, limited visible light absorption, and rapid recombination of photogenerated electron–hole pairs. Coupling multiple semiconductors enhances electron–hole separation, prolongs carrier lifetime, and improves interfacial charge transfer efficiency. Here, In2O3/CuO/g-C3N4 ternary composites are synthesized via thermal polymerization and characterized by using XRD, TEM, XPS, and UV–vis spectroscopy. The ternary composite achieves superior photogenerated carrier separation compared with In2O3/g-C3N4 and CuO/g-C3N4 binary composites. In photocatalytic CO2 reduction tests, In2O3/CuO/g-C3N4 demonstrates higher catalytic activity with a CO yield of 890.50 μmol/g/h and a 100% CO selectivity.