Three-dimensional electrode design with conductive fibers and ordered macropores for enhanced capacitive deionization performance

Abstract

Capacitive deionization (CDI) is a promising energy-efficient electrochemical water treatment technology and a scalable electrode having high mass loading is an essential imperative to the success of this technology. A thick CDI electrode was constructed by loading activated carbon particles as the electroactive material into a three-dimensional framework fabricated from a mixture felt of conductive carbon fiber serving as an electron transfer channel and removable yak hair functioning to provide an ion transport pathway. The carbon fiber reduces the electrode electrical resistance and the ultimately removed yak hair creates an ordered macropore array that provides an ion reservoir as well as a conduction channel for reducing ion transport distance inside the electrode. The resulting composite electrode with an optimal carbon fiber and yak hair content shows a specific capacitance of 219.27 F g−1 at 0.1 A g−1 and reaches salt adsorption capacity of 15.75 mg g−1 and average salt adsorption rate of 17.10 mg g−1 h−1 with more than 50% retention after 200 cycles. The designed three-dimensional composite exhibits enhanced deionization and long-term stability that is believed to be a low-cost and simple assembly solution for achieving a high mass loading and scalable electrode for the industrial CDI applications.