Influence of Headgroups in Ethylene-Tetrafluoroethylene-Based Radiation-Grafted Anion Exchange Membranes for CO2 Electrolysis

The performance of zero-gap CO2 electrolysis (CO2E) is significantly influenced by the membrane's chemical structure and physical properties due to its effects on the local reaction environment and water/ion transport. Radiation-grafted anion-exchange membranes (RG-AEM) have demonstrated high ionic conductivity and durability, making them a promising alternative for CO2E. These membranes were fabricated using two different thicknesses of ethylene-tetrafluoroethylene polymer substrates (25 and 50 mu m) and three different pyrrolidinium, and benzyl-N-methylpiperidinium (MPIP). Our membrane characterization and testing in zero-gap cells over Ag electrocatalysts under commercially relevant conditions showed correlations between the water uptake, ionic conductivity, hydration, and cationic-head groups with the CO2E efficiency. The thinner 25 mu m-based AEM with the MPIP-headgroup (ion-exchange capacities of 2.1 +/- 0.1 mmol g(-1)) provided balanced in situ test characteristics with lower cell potentials, high CO selectivity, reduced liquid product crossover, and enhanced water management while maintaining stable operation compared to the commercial AEMs. The CO2 electrolyzer with an MPIP-AEM operated for over 200 h at 150 mA cm(-2) with CO selectivities up to 80% and low cell potentials (around 3.1 V) while also demonstrating high conductivities and chemical stability during performance at elevated temperatures (above 60 degrees C).

Automated summary

The performance of zero-gap CO2 electrolysis (CO2E) depends on the membrane's chemical structure and physical properties. Radiation-grafted anion-exchange membranes (RG-AEM) show high ionic conductivity and durability, making them a promising alternative for CO2E. The thinner 25μm-based AEM with the MPIP-headgroup provided better CO2E efficiency in terms of lower cell potentials, high CO selectivity, reduced liquid product crossover, and enhanced water management.