Phosphorus Tailors the d-Band Center of Copper Atomic Sites for Efficient CO₂ Photoreduction under Visible-Light Irradiation

Photoreduction of CO₂ into solar fuels has received great interest, but suffers from low catalytic efficiency and poor selectivity. Herein, two single-Cu-atom catalysts with unique Cu configurations in phosphorus-doped carbon nitride (PCN), namely, Cu₁N₃@PCN and Cu₁P₃@PCN were fabricated via selective phosphidation, and tested in visible light-driven CO₂ reduction by H₂O without sacrificial agents. Cu₁N₃@PCN was exclusively active for CO production with a rate of 49.8 μmol_CO g_cat⁻¹ h⁻¹, outperforming most polymeric carbon nitride (C₃N₄) based catalysts, while Cu₁P₃@PCN preferably yielded H₂. Experimental and theoretical analysis suggested that doping P in C₃N₄ by replacing a corner C atom upshifted the d-band center of Cu in Cu₁N₃@PCN close to the Fermi level, which boosted the adsorption and activation of CO₂ on Cu₁N₃, making Cu₁N₃@PCN efficiently convert CO₂ to CO. In contrast, Cu₁P₃@PCN with a much lower Cu 3d electron energy exhibited negligible CO₂ adsorption, thereby preferring H₂ formation via photocatalytic H₂O splitting.