Capacitive deionization using a carbon electrode prepared with water-soluble poly(vinyl alcohol) binder

To increase the wettability of carbon electrodes, we have fabricated a carbon electrode using a poly(vinyl alcohol) (PVA) binder (a water-soluble polymer) by cross-linking PVA with glutaric acid (GA). The PVA-bonded carbon electrodes were prepared at various cross-linking temperatures and GA contents, and their electrochemical properties were analyzed using cyclic voltammetry (CV) and impedance spectroscopy. All carbon electrodes prepared in this study maintained their integrity within boiling water, which demonstrated the chemical stability of PVA cross-linking with GA. CV and impedance spectroscopy showed that the cross-linking temperature can significantly affect the resistance of PVA-bonded carbon electrodes by influencing the degree of cross-linking. The electric resistance increased with decreasing cross-linking temperature, which was attributed to the swelling of PVA that was permitted by inadequate cross-linking of PVA with GA at low temperatures. As the mole ratio of GA to PVA increased from 5 to 20 mol/mol, specific capacitance increased also; this behavior appeared to result from the unreacted GA, which carried a negative charge. The desalting performance of the carbon electrodes prepared in this study indicates that they are suitable for capacitive deionization applications.