Efficient ethylene electrosynthesis through C–O cleavage promoted by water dissociation

Abstract

Electrochemical reduction of carbon monoxide is a promising carbonate-free approach to produce ethylene using renewable electricity. However, the performance of this process suffers from low selectivity and energy efficiency. A priority has been to weaken water dissociation with the aim of inhibiting the competing hydrogen evolution reaction but when this path was examined by replacing H2O with D2O, a further-reduced selectivity toward ethylene was observed. Here we examine approaches to promote water adsorption and to decrease the energy barrier to the ensuing water dissociation step, which could promote C–O cleavage in *CHCOH hydrogenation to *CCH. We modified a copper catalyst with the strong electron acceptor 7,7,8,8-tetracyanoquinodimethane, which made the catalyst surface electron deficient. The observed ethylene Faradaic efficiency was 75%, 1.3 times greater than that of unmodified copper control catalysts. A full-cell energy efficiency of 32% was achieved for a total projected energy cost of 154 GJ t−1 in ethylene electrosynthesis in a membrane electrode assembly. CO electroreduction is a promising carbonate-free approach to produce ethylene, but suffers from limited selectivity and low energy efficiency. By modifying copper with a strong electron acceptor, 7,7,8,8-tetracyanoquinodimethane, the water dissociation step is accelerated, leading to excellent ethylene selectivity and full-cell energy efficiency in CO electroreduction.