Planar chlorination engineering induced symmetry-broken single-atom site catalyst for enhanced CO2 electroreduction

Abstract Breaking the geometric symmetry of traditional metal-N 4 sites and further boosting catalytic activity are significant but challenging. Herein, planar chlorination engineering is proposed for successfully converting the traditional Zn-N 4 site with low activity and selectivity for CO 2 reduction reaction (CO 2 RR) into highly active Zn-N 3 site with broken symmetry. The optimal catalyst Zn-SA/CNCl-1000 displays a highest faradaic efficiency for CO (FE CO ) around 97 ± 3% and good stability during 50 h test at high current density of 200 mA/cm 2 in zero-gap membrane electrode assembly (MEA) electrolyzer, with promising application in industrial catalysis. At -0.93 V vs. RHE, the partial current density of CO ( J CO ) and the turnover frequency (TOF) value catalyzed by Zn-SA/CNCl-1000 are 271.7 ± 1.4 mA/cm 2 and 29325 ± 151 h -1 , as high as 29 times and 83 times those of Zn-SA/CN-1000 without planar chlorination engineering. The in-situ extended X-ray absorption fine structure (EXAFS) measurements and density functional theory (DFT) calculation reveal the adjacent C-Cl bond induces the self-reconstruction of Zn-N 4 site into the highly active Zn-N 3 sites with broken symmetry, strengthening the adsorption of * COOH intermediate, and thus remarkably improving CO 2 RR activity.