Anion exchange membranes for electrochemical CO2 reduction

Electrochemical reduction of CO₂ towards fuels and chemicals (e.g. ethanol and ethylene) is a promising route to transition to a more sustainable chemical industry and close the carbon cycle. The electrochemical CO₂ reduction reaction (CO₂RR) is generally performed in reactors consisting of an anode and cathode on opposite sides of an anion exchange membrane (AEM) in an alkaline electrolyte solution (Figure 1). The AEM is a key component for CO₂ reduction and consists of a polymer backbone with positively charged groups. It should facilitate the transport of hydroxide ions between the anode and cathode while serving as a barrier between the two compartments.

While extensive research has been performed on optimizing the electrodes for CO₂RR, the AEM is less well studied and suffers from poor chemical and mechanical stability at high pH, low hydroxide conductivity and cross-over of negatively charged species. We aim to improve the understanding of membrane influences on the selectivity and efficiency of the CO₂RR. This insight will be used to develop a novel AEM with improved chemical stability, hydroxide conductivity and selectivity. Satisfying these requirements is challenging due to the trade-off between the membrane properties. Incorporating additives such as (functionalized) silica could improve the membrane stability without sacrificing the conductivity and selectivity.