Membrane-electrode assemblies for flow-electrode capacitive deionization

TL;DR

This paper introduces flexible membrane-electrode assemblies (MEAs) with carbon-fiber fabrics for flow-electrode capacitive deionization, enabling thinner membranes and improved electrochemical performance, thus addressing scale-up challenges.

Contribution

It presents a novel MEA design with carbon-fiber fabrics that allows for thinner ion-exchange membranes and enhanced desalination efficiency in flow-electrode capacitive deionization.

Findings

Salt transfer rates comparable to standard setups.

Thinner membranes reduce potential drop.

More homogeneous electric field improves performance.

Abstract

Scale-up of flow-electrode capacitive deionization is hindered due to the reliance on thick brittle graphite current collectors. Inspired by developments of electrochemical technologies we present the use of flexible membrane electrode assemblies (MEA) to solve these limitations. We tested different carbon-fiber fabrics as current collectors and laminated them successfully with ion-exchange membranes. The use of thinner ion-exchange membranes is now possible due to the reinforcement with the carbon fiber fabric. Desalination experiments reveal that a MEA setup can achieve salt transfer rates equal to standard setups. Hence, we deduce that charge percolation also acts outside the electric field. In a single point of contact, ionic and electric charges are exchanged at the carbon surface of the MEA. The use of thinner membranes leads to a reduced potential drop. Together with a more homogeneous electric field across the feed water section, this can compensate for the reduction of contact surface between flow electrode and current collector.