Continuous electroreduction of CO2 towards formate in gas-phase operation at high current densities with an anion exchange membrane

The carbon dioxide (CO2) electroreduction to formate is nowadays considered as a promising approach to convert CO2 into a value-added product and simultaneously, in the context of strategies for mitigating climate change. However, there is a scarce number of studies published in the literature operating with a current density higher than 200 mA cm−2, and there is the need of operating at higher current densities, with acceptable performance and low penalty in terms of energy consumption, for future implementation at industrial scale. Thus, in this work, a novel configuration is studied using a filter press reactor in a continuous mode, with a single pass of the reactants through the cell, employing a Sustainion anion exchange membrane and working with a current density up to 600 mA cm−2. Using the same electrocatalysts, the configuration shows a similar performance to the GDE configuration with liquid electrolyte, but with the advantage of operating only with a vapour input to the cathode and avoiding the need for a liquid catholyte. Although at the expense of obtaining a more diluted product, excellent combinations of Faradaic Efficiency for formate (73.7 %), energy consumptions (342 kWh·kmol-1), and product rates (22.9 mmol m−2·s-1) can be achieved at high current densities. Therefore, the configuration with Sustainion membranes reported in this manuscript can be particularly interesting for future applications that do not involve a very concentrated formate product.