Alkaline Ionic Liquid Microphase Promotes Deep Reduction of CO 2 on Copper.

Electrochemical reduction of CO 2 to multicarbon (C 2+ ) products using renewable energy sources is an important route to storing sustainable energy and achieving carbon neutrality. It remains a challenge to achieve high C 2+ product faraday efficiency (FE) at ampere-level current densities. Herein, we propose the immobilization of an alkaline ionic liquid on copper for promoting the deep reduction of CO 2 . By this strategy, a C 2+ FE of 81.4% can be achieved under a current density of 0.9 A·cm -2 with a half-cell energy conversion efficiency of 47.4% at -0.76 V vs reversible hydrogen electrode (RHE). Particularly, when the current density is as high as 1.8 A·cm -2 , the C 2+ FE reaches 71.6% at an applied potential of -1.31 V vs RHE. Mechanistic studies demonstrate that the alkaline ionic liquid plays multiple roles of improving the accumulation of CO 2 molecules on the copper surface, promoting the activation of the adsorbed CO 2 , reducing the energy barrier of CO dimerization, stabilizing intermediates, and facilitating the C 2+ product formation.