Modulating Electronic Density of Single-Atom Ni Center by Heteroatoms for Efficient CO₂ Electroreduction

Single-atom catalysts (SACs) with unique geometric and electronic configurations have triggered great interest in many important reactions. However, controllably modulating the electronic structure of metal centers to enhance catalytic performance remains a challenge. Here, the electronic structure of Ni centers over Ni₁-NC SACs by introducing electron-rich phosphorus or electron-deficient boron for electrochemical CO₂ reduction (CO₂RR) is systematically tailored. It is found that the Ni₁-PNC with Ni₁-N₃P site exhibits superior performance with a current density of 14.6 mA cm^-2 and a Faradaic efficiency of 90.6% at -0.8 V versus RHE for CO production, far exceeding Ni₁-NC and Ni₁-BNC SACs. Detailed characterizations and theoretical calculations reveal a linear relationship between the valence state of Ni species and the CO₂RR performance. The incorporation of P species facilitates the electronic localization around the Ni₁ center, significantly promoting the adsorption of CO₂ and the formation of key *COOH intermediate to enhance CO₂RR. This work provides a feasible approach to quantitatively manipulate the electronic structure of single-atom metal sites and to rationally design highly efficient catalysts for boosted performance.