Generating Long-Lived Charge Carriers in CdS Quantum Dots by Cu-Doping for Photocatalytic CO₂ Reduction

Converting CO₂ into high-value-added chemicals has been recognized as a promising way to tackle the fossil fuel crisis. Quantum dots (QDs) have been extensively studied for photocatalytic CO₂ reduction due to their excellent optoelectronic properties. However, most of the photogenerated charge carriers recombine before they participate in the photocatalytic reaction. It is crucial to regulate the charge carriers to minimize undesired charge recombination, thus, promoting surface photocatalysis. Herein, we report a copper-doped CdS (Cu:CdS) QD photocatalyst for CO₂ reduction. Density functional theory simulations and experimental results demonstrate that Cu dopants create intermediate energy levels in CdS QDs that can extend the lifetime of exciton charge carriers. Furthermore, the long-lived charge carriers can be harnessed for the photocatalytic reaction on Cu:CdS QDs. The resultant Cu:CdS QDs exhibited a significantly enhanced photocatalytic activity toward CO₂ reduction compared to the pristine CdS QDs. This work highlights the importance of charge regulation in photocatalysts and opens new pathways for the exploration of efficient QD photocatalysts.