Activated Carbon-Based Electrodes with Engineered Microstructure for Capacitive Deionization (CDI) of Aqueous Solutions

Abstract

Capacitive Deionization (CDI) is a relatively novel technique which uses an external electric field to remove ionic species from water streams and adsorb them onto a highly porous material. In this system, the interplay between the transport phenomena taking place in the microstructure of the porous electrode and in the bulk flow is of paramount importance as it determines the concentration profile of the effluent. Microporosity and tortuosity of the electrodes dictate the motion of the species in the porous medium and set its adsorption capacity and resistivity. In this work, to achieve systems with better electrosorption and energetic performance, activated carbon electrodes with engineered microtopology are manufactured by employing magnetic field manipulation. By properly arranging the location of the macropores, the fabricated materials allow ions to freely diffuse within the electrode. Along with the electrochemical characterization methods, adsorption and energetic efficiency of the manufactured electrodes are evaluated using the proposed comprehensive figure-of-merits. The obtained results provide new insights into the effects of porous geometry on the microscale electro-sorption and diffusion of ionic species within the porous electrode and their correlation with the macroscale advection and diffusion in the bulk flow of CDI units. The adopted manufacturing process also leads towards development of large-scale production of carbon-based electrodes with controlled microstructures for different applications.