Enhancing CO2 electroreduction over iron-nitrogen-doped carbon catalysts by axial bromine coordination

• Axial Br assisted single iron atom catalyst is designed for ECR to CO. • The introduction of Br to Fe contributes to the formation of more surface-active sites. • The optimal catalyst exhibits FE CO of 93.78% and J CO of -21.16 mA cm −2 at -0.9 V (vs. RHE). Axial coordination engineering is a promising method to regulate the active sites of single atom catalysts (SACs) in Electrochemical reduction of CO 2 (ECR) and further realize the manipulating of the electrocatalytic activity, selectivity, and stability of catalysts. Here, a facile post-synthetic modification strategy of metal exchange and heteroatom dopant was proposed to develop a single iron atom catalyst coordinated with four planar N atoms and one axial Br atom (denoted as Fe x -NCBr y ) for ECR to CO. By altering the operating conditions including pyrolysis temperature as well as dopant amount of Fe and Br, the optimized Fe 20 -NCBr 0.3 catalyst acquired more surface-active sites and lower impedance, exhibiting an enhanced CO selectivity of 93.78% with a CO reduction current density of -21.16 mA cm −2 at -0.9 V (vs. RHE). This work provides fresh possibilities for tuning the SACs coordination environment with an axial heteroatom for improved ECR performance.