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 CO₂ 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 CO₂ 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 cm² 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 CO₂ electrolysis cell scaled up to a 10 × 100 cm² cell stack is demonstrated as a step toward the development of an industrial-scale CO₂ electrolysis cell. These results suggest that the hydrophilic porous membrane is a promising diaphragm option for the practical application of CO₂ electrolyzers.