Activated Carbon-Embedded Reduced Graphene Oxide Electrodes for Capacitive Desalination

Abstract

Capacitive deionization of saline water is one of the most promising water purification technologies due to its high energy efficiency and cost-effectiveness. This study synthesizes porous carbon composites composed of reduced graphene oxide (rGO) and activated carbon (AC) with various rGO/AC ratios using a facile chemical method. Surface characterization of the rGO/AC composites shows a successful chemical reduction of GO to rGO and incorporation of AC into rGO. The optimized rGO/AC composite electrode exhibits a specific capacitance of ~243 F g<sup>−1</sup> in a 1 M NaCl solution. The galvanostatic charging-discharging test shows excellent reversible cycles, with a slight shortening in the cycle time from the ~260<sup>th</sup> to the 530<sup>th</sup> cycle. Various monovalent sodium salts (NaF, NaCl, NaBr, and NaI) and chloride salts (LiCl, NaCl, KCl, and CsCl) are deionized with the rGO/AC electrode pairs at a cell voltage of 1.3 V. Among them, NaI shows the highest specific adsorption capacity of ~22.2 mg g<sup>−1</sup>. Detailed surface characterization and electrochemical analyses are conducted.