Alkaline Ionic Liquid Microphase Promotes Deep Reduction of CO₂ on Copper

Abstract

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.

Green solvent systems for material syntheses and chemical reactions

“…Besides the above utilization of IL or IL-based solvents as an alternative to the commonly used electrolyte for electrocatalytic CO 2 reduction reaction, ILs have been used as modifiers for electrocatalysts to enhance the selectivities and activities. 142,143 Zhang's group proposed the anchoring of an IL on a Cu electrocatalyst to improve the efficiency of electrochemical CO 2 conversion (Fig. 8).…”

“…Furthermore, an alkaline IL (AIL) was immobilized on Cu to promote the deep reduction of CO 2 . 143 The AIL-modified Cu was obtained by electroreducing the pre-prepared Cu 2 O@AIL, where the AIL was 1-aminopropyl-3-methylimidazolium bromide ([C 3 NH 2 MIm]Br). The catalytic activity of the AIL-functionalized Cu for the electrochemical CO 2 reduction reaction was evaluated in a flow cell with 1.0 M KOH aqueous solution as the electrolyte.…”