Performance Enhancement of a Membrane Electrochemical Cell for CO 2 Capture

Abstract

The utilization of renewable electrons to capture and valorize CO 2 will be a critical component in achieving a net zero emission society. The deployment of electrochemically driven technologies will depend on whether they can operate efficiently and economically at scale. We have proposed an anion exchange membrane-based device to regenerate the alkalinity of a carbonate capture solution while simultaneously concentrating CO 2 in an H 2 stream. To improve the technology readiness, we have reduced overpotentials in the cell and increased the operating current density through design optimization of the cathode compartment. The use of targeted geometries to promote bubble evacuation from the cell, particularly for the cathode spacer, had a significant effect on reducing the cell voltage and enabled higher current density operation than what was previously attainable. Using a pure K 2 CO 3(aq) feed, the cell achieved a specific energy consumption of 290 kJ∙mol CO2 −1 at 100 mA∙cm −2 , with a faradaic efficiency of 45% (90% CO 3 2− transport). The specific energy consumption reached a minimum at moderate current densities (∼50 mA∙cm −2 ), with a cell voltage of ∼1 V. This work shows that reasonable specific energy consumption at industrially relevant current densities can be enabled through cell design, material selection, and effective management of bubbles.