Engineering Cu–Co Active Sites in CdIn2S4 for Selective CO2 Photoreduction to CH4

Single-metal doping in photocatalysts can lead to a trade-off between activity and product selectivity. Here, Cu–Co codoping was introduced into CdIn2S4 to regulate the electronic structure and surface reaction properties. The Cu–Co codoping modulates sulfur vacancy concentration, introduces impurity states, and generates surface active sites. These structural modifications broaden visible-light absorption and facilitate charge separation and transfer. The Cu–Co active sites enhance CO2 adsorption and promote the formation of bridging M–C–O–M intermediates, thereby directing CO2 reduction toward CH4 formation. With a selectivity of 99.55%, the optimized catalyst produces CH4 at a rate of 116.58 μmol·g–1·h–1 under visible-light irradiation.