Fabrication and characterization of a carbon electrode coated with cation-exchange polymer for the membrane capacitive deionization applications

A carbon electrode coated with cation-exchange polymer was fabricated in a simple and inexpensive way for applications in membrane capacitive deionization (MCDI). A mixture of poly(vinyl alcohol) (PVA) and sulfosuccinic acid (SSA) was used as a coating solution to introduce negatively charged ion-exchange groups. The PVA/SSA-coated carbon electrodes were fabricated at different crosslinking temperatures and SSA contents. The prepared electrodes were characterized by SEM, FTIR analysis, cyclic voltammetry and electrical impedance spectroscopy. The PVA/SSA coating layer showed high adhesion to the carbon powders. The SSA was effectively introduced as a crosslinking agent and cation-exchange groups, as shown in the FTIR spectra. Cyclic voltammetry analysis indicated that the specific capacitance was increased by coating the carbon electrode with PVA/SSA polymer solution. The specific capacitances of the coated electrode were enhanced by 14.8–30.9% compared with the uncoated one, depending on the crosslinking temperature. The increased capacitance of the coated electrode is attributed to the fixed ion concentration in the PVA/SSA coating layer. The electric resistance and specific capacitance of the coated carbon electrodes were affected strongly by the crosslinking temperature due to the altered degree of crosslinking. The area resistances of the coating layer were in the range of 0.67–1.17 Ω cm2, depending on the crosslinking temperature and SSA content, which is relatively low when compared with commercial ion-exchange membranes.