Highly Selective Acetylene‐to‐Ethylene Electroreduction Over Cd‐Decorated Cu Catalyst with Efficiently Inhibited Carbon‐Carbon Coupling

Abstract Electrochemical acetylene reduction (EAR) employing Cu catalysts represents an environmentally friendly and cost‐effective method for ethylene production and purification. However, Cu‐based catalysts encounter product selectivity issues stemming from carbon‐carbon coupling and other side reactions. We explored the use of secondary metals to modify Cu‐based catalysts and identified Cd decoration as particular effective. Cd decoration demonstrated a high ethylene Faradaic efficiency (FE) of 98.38 % with well‐inhibited carbon‐carbon coupling reactions (0.06 % for butadiene FE at −0.5 V versus reversible hydrogen electrode) in a 5 vol % acetylene gas feed. Notably, ethylene selectivity of 99.99 % was achieved in the crude ethylene feed during prolonged stability tests. Theoretical calculations revealed that Cd metal accelerates the water dissociation on neighboring Cu surfaces allowing more H* to participate in the acetylene semi‐hydrogenation, while increasing the energy barrier for carbon‐carbon coupling, thereby contributing to a high ethylene semi‐hydrogenation efficiency and significant inhibition of carbon‐carbon coupling. This study provides a paradigm for a deeper understanding of secondary metals in regulating the product selectivity of EAR electrocatalysts.