Regulating the coordination environment of single-atom catalysts for electrocatalytic CO₂ reduction

Electrochemical CO₂ reduction (ECR) through single-atom catalysts (SACs) consisting of transition metals (TMs) anchored on nitrogenated carbon (TM-N-C) has shown promise for carbon neutralization. However, high overpotentials and low selectivity are still issues. Regulating the coordination environment of anchored TM atom is important to address these problems. In this study, we evaluated nonmetal atom (NM = B, O, F, Si, P, S, Cl, As and Se) modified TM (TM = Fe, Co, Ni, Cu and Zn)@N₄-C catalysts for their ECR to CO performance using density functional theory (DFT) calculations. NM dopants can induce active center distortion and tune electron structure, promoting intermediate formation. Doping heteroatoms can improve ECR to CO activity on Ni and Cu@N₄ but worsen it on Co@N₄ catalysts. Fe@N₄-F₁(I), Ni@N₃-B₁, Cu@N₄-O₁(III), and Zn@N₄-Cl₁(II) have excellent activity for ECR to CO, with overpotentials of 0.75, 0.49, 0.43, and 0.15 V, respectively, and improved selectivity. The catalytic performance is related to the intermediate binding strength, as evidenced by d band center, charge density difference, crystal orbital Hamilton population (COHP), and integrated COHP (ICOHP). It is expected that our work can be used as the design principle to guide the synthesis of the high-performance heteroatoms modified SACs for ECR to CO.