Photocatalytic CO2 Reduction to CO over Ni Single Atoms Supported on Defect-Rich Zirconia

The photocatalytic CO2 reduction reaction (CRR) holds great promise for curbing anthropogenic CO2 emissions, though boosting photocatalyst activity and tuning product selectivity remain key priorities. Herein, isolated Ni single atoms dispersed on defect rich zirconia (Ni-SA-x/ZrO2) are identified as a very promising photocatalyst for CRR under Xe lamp irradiation, showing good activity and CO selectivity in the absence of added sacrificial agents or sensitizers. Due to an abundance of accessible nickel single atomic sites, the optimized photocatalyst affords CO at a rate of 11.8 mu mol g(-1) h(-1) (92.5% selectivity). Experimental and theoretical investigations determine that the atomically dispersed Ni sites lower the energy barrier for CO2 to CO conversion via an adsorbed COOH intermediate, while also suppressing H-2 desorption in the competing water splitting reaction. The Ni single atom sites thus simultaneously promote CO2 conversion and CO selectivity, thus offering valuable new insights for the future design of improved metal single-atom catalysts for CRR.