Once the electrodialysis cell was assembled, a peristaltic pump (Ismatec ISM4408) was used to flow 1 M NaOH (10 mL min -1 ) through the outer chambers, 3 M NaCl (10 mL min -1 ) through the dilute chamber (chamber between CEM and AEM), and the relevant bicarbonate, carbonate, or simulated seawater solution (0.2 mL min -1 ) through the chambers on either side of the BPM. These flowrates remained constant through all measurements. Once all chambers were filled, leads from a SP-300 BioLogic potentiostat were connected to the cathode, anode, and reference electrodes in a four-point measurement configuration. Current density-voltage measurements were then obtained by applying a chosen current across the cathode and anode and measuring the voltage between the two Ag/AgCl reference electrodes. Oxygen evolution was performed at the anode and hydrogen evolution was performed at the cathode. These reactions were isolated from the BPM with the two monopolar membranes positioned on either side. Measurements were started at 0.1 mA cm -2 and increased stepwise through each current density to 100 mA cm -2 (EC-lab® software). Each current step was held constant for 20 minutes to obtain a steady-state voltage.