Improved capacitive deionization of sulfonated carbon/titania hybrid electrode

Abstract The surface of commercially-available activated carbon (AC) was functionalized through the TiO 2 coating and sulfonation, and the resulting powder was evaluated as a capacitive deionization (CDI) electrode. TiO 2 coating on the AC surface was achieved by a sol-gel method and followed by the sulfonation using Tiron. From the cyclic voltammetry and the electrochemical impedance analysis, the TiO 2 coating and sulfonation improved specific capacitance and reduced ion diffusion resistance. To achieve improvement in the desalination performance, it was fond that the AC-Ti or AC-Ti-S electrode was used as a negative electrode rather than a positive electrode. This result was well explained by shifting the potential of zero charge (E PZC ) from 0.15 V (pristine AC) to 0.25 (AC-Ti) or 0.35 V (AC-Ti-S). Finally, the specific adsorption capacity (SAC) of the AC-Ti-S electrode was improved about 1.5 times higher than that of the pristine AC electrode. Also, the charging efficiency was improved from 61% (pristine AC) to 84% via the TiO 2 coating and sulfonation, which was due to the increase of wettability and the reduction of co-ion repulsion effect.