Modulating Electrochemical CO ₂ Reduction Pathways via Interfacial Electric Field

Copper (Cu) is a versatile electrocatalyst for the carbon dioxide reduction reaction (CO 2 RR), capable of generating various hydrocarbons. While this versatility is advantageous, controlling product selectivity remains a major challenge. Conventional Cu‐based electrodes often favor ethylene production, limiting the selectivity for other products such as methane. Here, the interfacial electric field is systematically engineered to direct the CO 2 RR pathway from ethylene toward methane production. Through extensive analysis, it is demonstrated that combining Cu and indium tin oxide (ITO) creates an interfacial electric field within the Cu/ITO electrode, ideal for altering the CO 2 RR pathway. This facilitates electron transfer from Cu to ITO, inducing a positive charge on the Cu species, which shifts the selectivity from ethylene to methane. While p ‐block elements such as tin (Sn) and indium (In) predominantly yield formate, and Cu is selective toward ethylene, the Cu/ITO catalyst demonstrates a methane production rate that exceeds that of Cu by over 50‐fold. This result highlights the substantial potential of engineering the interfacial electric field to control electrocatalytic reaction pathways. Computational analyses using DFT calculations revealed the significant electronic charge transfer between the Cu surfaces and the In and Sn sites which agrees well with the spectroscopic measurements of interfacial electric field.