Recent developments in ion conductive membranes for CO2 electrochemical reduction

The conversion of CO2 into good value fuel through CO2 reduction reaction (CO2RR) is promising to mitigate the energy crisis and greenhouse effect for a carbon–neutral economy. To this end, tremendous research and development have so far been devoted to the design of new high-performance electrocatalysts and electrochemical reactors. However, the impact of ion conductive membranes (ICMs) on conversion efficiency has received little attention. The final performance of CO2RR systems is strongly linked to the properties of ion conductive membranes in terms of ionic conductivity, selectivity, water absorption, and stability. However, numerous obstacles must be overcome in ICMs of CO2RR systems, including the balance of various properties of ICMs, the undesired crossover of products and reactants across the membrane, and the local acidic pH environment at the cathode. In this review, we highlight the importance and function of membranes and provide a first comprehensive analysis of the types of membranes reported for CO2RR systems. The compositions of various types of membranes were examined, and their advantages and disadvantages were compared. The mechanisms of ion transport in different membranes were then analyzed, and future challenges and prospects of ion conductive membranes in CO2RR were provided. This review aims to provide important guidance for the design of CO2RR membranes.