Efficient and stable operation of capacitive deionization assessed by electrode and membrane asymmetry

Capacitive deionization (CDI) is an electrochemical technology emerging as a cost-effective alternative for desalination of brackish water. Despite the remarkable advances in terms of salt adsorption capacity ( SAC ) and charge efficiency (QE), there are still challenging issues concerning the electrode stability for long-term operation. Here, we report a comprehensive study of how different cell configurations (asymmetry and membrane CDI) and voltages affect the desalination capacity and the stability of the activated carbons (AC) derived from p-toluenesulfonate-or sulfate-doped polyaniline (PAC/PTS or PAC/S, respectively). It was demonstrated that the electrochemical and textural properties of these materials have a major influence on the electrode stability. The control of the potential distribution in asymmetric cells is pointed out as an effective strategy to suppress the carbon oxidation reactions responsible for the SAC loss, and improve the long-term stability. The best desalination performance was achieved using PAC/PTS electrodes in a MCDI configuration. A remarkable value of SAC similar to 32 mg g(-1) at 1.2 V), along with 100% of SAC retention was observed over 100 cycles. Our findings enable a better understanding of how to mitigate undesirable faradaic reactions and improve the long-term stability of PAC electrodes, thus providing promising electrodes for water desalination. (C) 2021 Elsevier Ltd. All rights reserved.