Cu2O Nano‐Homojunction for High‐Efficiency Electrocatalytic CO2‐to‐Ethylene Conversion

The efficient electrochemical CO2 reduction into value‐added multi‐carbon products is of great importance and remains challenging. Here, we demonstrate the highly selective, active and long‐term durable electrocatalytic production of ethylene from CO2 by constructing a Cu2O nano‐homojunction, which is composed of Cu2O nanocubes in size of ~100 nm and the surface‐adhered Cu2O nanodots in size of ~12 nm, as electrocatalyst. The maximum Faradaic efficiency of ethylene can reach 73.7% at −1.4 V versus reversible hydrogen electrode in H‐type cell, with partial current density to ethylene of 38.2 mA cm−2. Moreover, it can work stably for more than 200 h at 0.31 A cm−2 in membrane electrode assembly. The mechanism for the high selectivity, activity and stability for CO2‐to‐ethylene conversion was investigated by in‐situ experiments and theoretical calculations. The results reveal that such a catalyst is efficient in adsorbing CO2, stabilizing the key intermediate *CO, and facilitating both the *CO protonation to form *CHO and the subsequent *CO‐*CHO coupling for ethylene formation.