Carbon electrode modified by KOH solution to improve performance of capacitive desalination

Abstract

A carbon electrode was modified by different concentrations of KOH solution to enhance its capacitive deionization performance. The hydrophilicity and electrochemical properties of the carbon electrode were characterized by FTIR analysis, contact angle test, cyclic voltammetry, and impedance spectroscopy analysis. The results show that contact angles of the carbon electrode decrease from 115° to 62° with an increase in the concentrations of KOH, indicating an increase in the hydrophilicity. The specific capacitance of carbon electrode achieves the maximum of 108.8 Fg−1 when modified by 5% KOH solution. Furthermore, desalination experiments were carried out in a lab-scale experimental system. The salt-removal efficiency of the modified carbon electrode increases by 23% under the conditions of 2.5 V applied voltage, initial concentration of 1,500 μs/cm, and flow rate of 20 ml/min. Thus, the capacitive deionization performance of the carbon electrode is significantly improved by the modification with KOH. This enhanced performance can be attributed to the hydroxyl functional groups introduced on to the surface of the carbon electrode and an increased wettability of the surface. Our results indicate that the KOH-modified carbon electrode will have great potential in the capacitive deionization technology.