Membrane-free electrochemical CO2 conversion using serially connected porous flow-through electrodes

Bicarbonate electrolysis offers a promising approach to conducting electrochemical carbon dioxide (CO2) conversion using aqueous carbon capture solutions as the electrolyte. However, conventional membrane-based electrolyzers face risks associated with membrane degradation as well as challenges to scale up that arise from concentration gradients that develop laterally along electrodes as the electrolyte flows parallel to their surfaces. Herein, we present a membrane-free electrolyzer concept based on porous flow-through electrodes for which the aqueous bicarbonate electrolyte flows sequentially through alternating cathodes and anodes. As shown by colorimetric imaging recorded during electrolysis, this configuration facilitates rapid re-balancing of pH between adjacent electrodes while promoting in situ generation of CO2 immediately upstream of cathodes. Results also show that CO2 utilization increases monotonically with the number of cells incorporated into a multi-cell device, and modeling predicts that CO2 utilization rates >80% are possible for optimized multi-cell devices.