A TiO2 nanofiber/activated carbon composite as a novel effective electrode material for capacitive deionization of brackish water

Abstract

Based on its excellent characteristics, high surface area, environmentally safe and availability in nature; activated carbon (AC) is the best candidate as a capacitive deionization (CDI) electrode material. Among the various modification methods for AC, incorporation of TiO₂ nanoparticles into the activated carbon proved to be an effective approach to enhance the desalination performance. Compared to the nanoparticulate morphology, nanofibers have a large axial ratio which provides a better electrosorption performance. Herein, for the first time, TiO₂ nanofibers (TNFs) prepared by the electrospinning process were exploited with activated carbon to form a hybrid network electrode for capacitive deionization. The phase morphology and crystal structure were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The electrochemical behavior was evaluated by cyclic voltammetry (CV). Furthermore, the desalination performances under different applied voltages and salty water concentrations were investigated using a prototype CDI unit in a continuous mode water flow. The results indicated that the electrode prepared from 10 wt% nanofibers (ACTNF 10%) exhibits the best results compared to other electrodes having 5 and 15 wt% TiO₂ nanofibers. Typically, the best electrode networks showed very good specific capacitance (380 F g⁻¹), excellent electrosorptive capacity (17.7 mg per g_carbon) at a cell potential of 1.2 V and an initial NaCl concentration of 292 mg L⁻¹, and a distinguished salt removal efficiency (∼89.6%). Moreover, the introduced electrode shows interesting recyclability and easy full regeneration.