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.