Promoting CO2 electroreduction to C2H4 product by promoting water molecules activation on MgO/CuO catalyst

Abstract

Electrocatalytic CO 2 reduction reaction (CO 2 RR) to ethylene (C 2 H 4 ) represents a promising approach to reducing CO 2 emissions and producing high-value chemicals. The ethylene productivity is always limited by the slow reaction kinetics and the high-performance catalysts are significantly desired. Many efforts have been made to develop a catalyst to activate CO 2 molecules. However, as another reactant, H 2 O activation does not receive the attention it deserves. In particular, slow H 2 O dissociation kinetics limit the rate of proton supply, severely impairing the production of C 2 H 4 . Here, we designed a MgO-modified CuO catalyst (MgO/CuO), which can promote H 2 O dissociation and enhance CO 2 adsorption at the same time to realize the efficient ethylene production. The optimal catalyst exhibits a Faraday efficiency for C 2 H 4 reached 54.4% at −1.4 V vs . RHE in an H-cell, which is 1.4 times that of pure CuO (37.9%), and it was further enhanced to a 56.7% in a flow cell, with a high current density of up to 535.9 mA cm −2 at −1.0 V vs . RHE. Experimental and theoretical calculations show that MgO/CuO plays a bifunctional role in the CO 2 RR, which facilitates the adsorption and activation of CO 2 by CuO and simultaneously accelerates H 2 O dissociation by MgO doping. The in situ XRD experiments demonstrate that the introduction of MgO protects CuO active phase to avoid overreduction and preserves the active centers for CO 2 RR. In combination with in situ FTIR and DFT calculations, the protonation process from *CO to *COH and asymmetric C–C coupling step are promoted by the enhanced water activation and proton coupling on MgO/CuO. This work provides new insights into the CO 2 and H 2 O coactivation mechanism in CO 2 RR and a potential universal strategy to design ethylene production electrocatalysts.

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