Chlorine‐Coordinated Unsaturated Ni–N₂ Sites for Efficient Electrochemical Carbon Dioxide Reduction

Abstract

Heteroatom‐doping is an effective method for modifying the geometric symmetry of metal–nitrogen–carbon (M–N–C) single‐atom catalysts and thereby tuning the electronic structure. Up to now, most of the current reports have concentrated on introducing heteroatoms into the highly symmetrical M–N₄ structure. The coordination‐unsaturated M–N₂ structure is more sterically favorable for the insertion of alien atoms to optimize the electronic structure. Herein, a Ni–N₂ catalyst with out‐of‐plane coordinated chlorine (Cl) atoms (Ni–N₂Cl/C) is successfully constructed on chlorine‐functionalized carbon supports (C–Cl) for an efficient carbon dioxide reduction reaction (CO₂RR). Density functional theory calculations demonstrate that the prepared Ni–N₂Cl/C catalyst exhibits a higher capability in balancing COOH* formation and CO* desorption. In addition, in situ Raman spectra confirm that the lower CO binding energy on the Ni–N₂Cl/C facilitates CO escape, leading to excellent CO₂RR performance. A high CO Faradaic efficiency (FE_CO) of more than 80% is achieved from −0.6 to −1.2 V versus reversible hydrogen electrode on the Ni–N₂Cl/C and it exhibits negligible FE_CO and current declination over a 40‐h stability test. Furthermore, a high turnover frequency (TOF) value of 15 808 h⁻¹ is obtained, which is more than ten times that of Ni–N₂/C (1476 h⁻¹) without coordinated Cl atoms.