Importance of Mass Loadings of Activated Carbon Electrode on Capacitive Deionization Performance

Abstract

Capacitive deionization is a promising electrochemical water treatment technology and activated carbon has been one of the most widely applied electrode materials with its parameters having an important influence on the electrosorption performance. In this work, on account of the mass loadings of the electrodes (the thickness varies from 200 μm to 600 μm), symmetric and asymmetric cells are constructed to investigate the importance of mass loadings on electrochemical performance and desalination. The results show that the electrode with the thickness of 200 μm achieves the largest specific capacitance of 72.65 F g-1, and thicker electrodes in the symmetric cell can reach a lower specific capacitance. However, the electrochemical performance of a working electrode in an asymmetric cell can be improved with a thicker counter electrode. As for desalination performance in the symmetric cell, S200 achieves the highest salt adsorption capacity of 7.05 mg g-1 under 1V cell voltage, and ion removal rate increases while electrode utilization reduces with increased mass loading. In an asymmetric cell, when the anode is fixed at 400 μm and the cathode thickness increases from 200 to 600 μm, the salt adsorption capacity, average salt adsorption rate and charge efficiency decreases from 6.33 mg g-1, 0.49 mg g-1 min-1, 44.77% to 3.27mg g-1, 0.17 mg g-1 min-1, 16.14%, respectively (dropped by 48.34%, 65.31% and 63.95%, respectively). The oxidation status of the electrode surface as characterized by XPS, FTIR, EDX et al., indicates that the oxidation degree of the anode can be reduced with a thinner cathode. Ultimately, lowering the mass loading of the cathode is conducive to enhancing total desalination performance and cycling stability.