Neighboring effects of single-atom cobalt enable high-performance CO2 photoreduction†

Herein, we demonstrate the unique neighboring effect of single-cobalt active sites anchored on BiOCl nanosheets with high CO₂ photoreduction performances by combining in situ X-ray photoelectron with in situ infrared spectroscopy. More specifically, single-atom Co sites demonstrate an exceptional electron-enriched feature from adjacent Bi atoms, which facilitates the formation of *CO₂–Co and *H₂O–Bi species, respectively. Under light irradiation, the photoinduced electron transfer from adjacent Bi atoms to single Co active sites is favorable for the formation *COOH and *CO intermediates, accompanied by the oxidation of H₂O molecules into *OH and *OOH species on Bi sites. As a result, these dynamic electronic interactions between single-atom Co and adjacent Bi sites are responsible for a record CO evolution activity of 172.6 μmol g⁻¹ h⁻¹ under sunlight illumination, which exceeds that of pristine BiOCl by nearly one order of magnitude. These findings provide a fundamental understanding of the intrinsic neighboring effect between single-atom sites and adjacent atoms, which should be crucial and essential for the development of high-performance single-atom catalysts.