Role of ion-selective membranes in the carbon balance for CO2electroreduction via gas diffusion electrode reactor designs

In this work, the effect of ion-selective membranes on the detailed carbon balance was systematically analyzed for high-rate CO(2)reduction in GDE-type flow electrolyzers. By using different ion-selective membranes, we show nearly identical catalytic selectivity for CO(2)reduction, which is primarily due to a similar local reaction environment created at the cathode/electrolyte interfaceviathe introduction of a catholyte layer. In addition, based on a systematic exploration of gases released from electrolytes and the dynamic change of electrolyte speciation, we demonstrate the explicit discrepancy in carbon balance paths for the captured CO(2)at the cathode/catholyte interfaceviareaction with OH(-)when using different ion-selective membranes: (i) the captured CO(2)could be transported through an anion exchange membrane in the form of CO32-, subsequently releasing CO(2)along with O(2)in the anolyte, and (ii) with a cation exchange membrane, the captured CO(2)would be accumulated in the catholyte in the form of CO32-, while (iii) with the use of a bipolar membrane, the captured CO(2)could be released at the catholyte/membrane interface in the form of gaseous CO2. The unique carbon balance path for each type of membrane is linked to ion species transported through the membranes.