Chlorine-induced mixed valence of CuOx/C to promote the electroreduction of carbon dioxide to ethylene

Electrochemical conversion of CO2 (CO2RR) into high-value fuel is identified as one of the promising approaches to achieve carbon neutrality. The synthesis of high-efficiency CO2 reduction electrocatalysts with high C2:C1, selectivity remains a field of intense interest. Previous studies have shown that the presence of Cu(I) is beneficial for the reduction of CO2 into C2 products. However, the stable presence of Cu(I) remains controversial, especially in the negative potential window. Here we report a simple and easily scalable catalyst precursor Cu2(OH)3Cl/C, which automatically forms in-situ chlorine-doped Cu/Cu2O heterointerface during electrocatalysis. The catalyst not only exhibits a Faradaic efficiency of 33.03% but also provides a long-term stability of Cu+, gaining a stable electrolysis of 11 h, with an ethylene/methane ratio over 50. The experimental results and mechanistic studies confirm that the presence of Cl− inhibits the reduction of Cu+, inducing the formation of Cu0/Cu+, and reduces the reaction energy of the intermediate ⋆CO dimerization, thereby facilitating the formation of C2 products. This work provides a feasible way to synthesize copper ions with long-term and stable positive charge in CO2RR and expands a new way to synthesize ethylene industrial products in the future.