Sub-millibar pressure gradient along a gravity-driven percolated CO2 gas diffusion electrode for vertical scale-up

Abstract

Herein the operating principles of a carbon dioxide electrolyser employing a percolator material and a gravity-fed electrolyte are demonstrated. By precisely adjusting reservoir elevations, the catholyte pressure profile applied to the CO₂ gas diffusion electrode as a function of height is deliberately manipulated. This approach enables the control of pressure differentials across the entire electrode, and the mitigation of hydrostatic pressure accumulation within the catholyte which would otherwise exceed the limited pressure resilience of current electrodes. To rationalise the fluid physics of operation, a tractable model that predicts the internal pressure profile within the percolator was developed, requiring only simple reservoir height adjustments to account for head losses specific to the electrolyser architecture. To validate and apply this model, a 32 cm tall electrolyser with vertical differential pressure monitoring was employed, demonstrating sub-millibar pressure gradients during operation. Under these conditions, stable CO₂ electrolysis was achieved, demonstrating the prospect of vertically scaled systems which is critical for industrial implementation.