Development of High‐Performance Zero‐Gap Carbon Dioxide Electrolysis Cells Using a Hydrophilic Porous Membrane

Abstract A hydrophilic porous membrane is adopted as the diaphragm in zero‐gap CO 2 electrolysis cells in order to improve their efficiency and durability. The hydrophilic porous membrane is sparse and nonpolar, which are features opposite to those seen in the anion‐exchange membranes commonly used as the diaphragm in CO 2 electrolysis cells. These characteristics result in high ion permeability and water penetration, which contribute to decreased power consumption and prevention of salt precipitation. A cell with an active area of 16 cm 2 is found to achieve a high Faradaic efficiency of 90% at a current density of 1000 mA cm −2 and a lower cell voltage compared with anion‐exchange membranes by applying pressure to prevent gas/liquid crossover. The energy efficiency attained ≈50% at 200 mA cm −2 under neutral electrolyte conditions. The cell exhibits excellent durability against the introduction of impurity gases, with no serious decreases in efficiency found in a 1000 h test at 400 mA cm −2 . Furthermore, a CO 2 electrolysis cell scaled up to a 10 × 100 cm 2 cell stack is demonstrated as a step toward the development of an industrial‐scale CO 2 electrolysis cell. These results suggest that the hydrophilic porous membrane is a promising diaphragm option for the practical application of CO 2 electrolyzers.