Fluorine‐Tuned Atomically Dispersed Magnesium Sites for Highly Efficient CO 2 Electrocatalytic Reduction

Abstract The electrochemical carbon dioxide reduction reaction (CO 2 RR) represents a promising strategy for converting CO 2 into CO. Atomically dispersed transition metal sites have an exceptional ability to activate CO 2 . However, the strong hybridization between the 3 d orbitals of these transition metals and the 5σ or 2π * orbital of CO significantly impedes * CO desorption, thereby limiting the overall CO generation activity. In contrast, s ‐block metals, with diffuse 3 s electron clouds, exhibit weaker interactions with * CO. Nevertheless, their practical application is hindered by the high energy barrier associated with the formation of the * COOH intermediate. To address these challenges, a fluorine(F)‐tuned magnesium single‐atom catalyst (Mg‐SAC) is developed. Remarkably, this catalyst achieved a CO Faraday efficiency of 97.3% and a current density of 260.4 mA cm −2 at −0.4 V vs the reversible hydrogen electrode in a flow cell, surpassing the performance of most state‐of‐the‐art SACs and transition metal catalysts reported in the literature. Mechanistic studies reveal that * CO desorption on Mg sites is significantly easier compared to that on Fe and Co sites. Furthermore, the incorporation of F atoms modifies the electronic structure of the MgN 4 sites, substantially lowering the energy barrier for the formation of the critical * COOH intermediate.