Residual Chlorine Induced Cationic Active Species on a Porous Copper Electrocatalyst for Highly Stable Electrochemical CO 2 Reduction to C 2+

Electrochemical carbon dioxide (CO 2 ) reduction reaction (CO 2 RR) is an attractive approach to deal with the emission of CO 2 and to produce valuable fuels and chemicals in a carbon‐neutral way. Many efforts have been devoted to boost the activity and selectivity of high‐value multicarbon products (C 2+ ) on Cu‐based electrocatalysts. However, Cu‐based CO 2 RR electrocatalysts suffer from poor catalytic stability mainly due to the structural degradation and loss of active species under CO 2 RR condition. To date, most reported Cu‐based electrocatalysts present stabilities over dozens of hours, which limits the advance of Cu‐based electrocatalysts for CO 2 RR. Herein, a porous chlorine‐doped Cu electrocatalyst exhibits high C 2+ Faradaic efficiency (FE) of 53.8 % at −1.00 V versus reversible hydrogen electrode (V RHE ). Importantly, the catalyst exhibited an outstanding catalytic stability in long‐term electrocatalysis over 240 h. Experimental results show that the chlorine‐induced stable cationic Cu 0 /Cu + species and the well‐preserved structure with abundant active sites are critical to the high FE of C 2+ in the long‐term run of electrochemical CO 2 reduction.