Enhanced desalination performance of anion-exchange membrane capacitive deionization via effectively utilizing cathode oxidation

To improve the long-term stability of capacitive deionization (CDI), one effective strategy is to introduce ion-exchange membranes into CDI (called as MCDI) owing to their ability to separate electrodes from oxidants. However, detailed explorations on the electrode corrosion in MCDI are seldom reported up to now. In this work, we studied in details the cathode oxidation in an anion-exchange membrane CDI (AEM-CDI) by employing activated carbon (AC) anode and different cathodes, AC and carbon sphere (CS). The results show that the anodes display a slight change during long cycling due to the isolation effect of AEM. However, the electrosorption capacity of AC cathode is slowly reduced, while CS cathode exhibits an improved electrosorption ability during the long-term operation. By analyzing the structure, morphology and element variations of original and cycled cathodes, it is found that both of specific surface area (SSA) and zero charge potential (E_pzc) of AC cathode are reduced, while CS cathode exhibits an enhanced SSA and E_pzc, indicating that the desalination performance of AEM-CDI cell, even with cathode materials with low E_pzc value and SAA, can be enhanced via effectively utilizing cathode oxidization.