Synergistic effects of ionic and nonionic surfactants treatment on activated carbon electrodes for inverted capacitive deionization

Abstract

Application of surfactants has attracted great interest in capacitive technologies owing to their potent interfacial activity. However, the reported surfactants utilization on Capacitive Deionization (CDI) technology is limited to ionic catalog. Herein, we reported a significant enhancement of capacitive behaviors by functionalizing inverted CDI (i-CDI) electrodes with dual surfactants, wherein nonionic surfactant induces synergistic effects with ionic surfactants. Brunauer-Emmett-Teller (BET) and Discrete Fourier Transform (DFT) isotherms analysis demonstrates that the surfactants loading reduce the pore volume and specific surface of activated carbon (AC) in accordance with the amount uptake. X-ray photoelectron spectroscopy (XPS) analysis shows the surfactant distribution within AC and its surface chemistry. The high resolution XPS spectra show the surfactants influence on binding energy and nitrogen is the most sensitive. The contact angle testing unveiled the fine wettability pertains on Tween 80. The surface charge evaluation in the context of Zeta potential measurement is presented. Through multiple electrochemical characterizations, dual surfactants treated electrodes display a superior capacitive behavior at a wide working voltage window. As such, the AC-T80-HDTMA/AC-T80-SDS system exhibits a higher salts removal capacity (7.5 mg g−1) with extended cyclic stability (38%) compare with AC-HDTMA/AC-SDS system (5.2 mg g−1) at 1.2 V. This work discloses profitable effects of ionic and nonionic surfactants synergy on i-CDI electrodes performance.