Enhancing Performance of Capacitive Deionization Under High Voltage by Suppressing Anode Oxidation Using a Novel Membrane Coating Electrode

High voltage operation is effective to improve salt adsorption capacity (SAC) of capacitive deionization (CDI), while this will cause performance loss during long-term operation. Herein, to address this issue, we report a simple approach to prepare novel membrane coating electrode (MCE) that polyvinyl alcohol/polyethyleneimine membrane was deposited onto activated carbon fiber (ACF) and glutaraldehyde (GA) was used for crosslinking. MCE with optimized GA concentration of 5% (MCE (5)) showed an improved SAC from 14.6 to 28.4 mg/g and stable charge efficiency at 80.2% when voltage increased from 0.8 V to high voltage of 1.8 V, showing better desalination performance than ACF (SAC: 13.2 to 20.9 mg/g, charge efficiency: 63.6% to 43.9%) due to suppressed anode oxidation. After forty cycles experiments at 1.8 V, SAC retention of ACF declined to 71.6% due to degradation of electrode properties, while SAC retention of MCE (5) increased to 124.7%. Membrane on MCE (5) was found to act as a barrier and corrosion inhibitor to restrict ACF oxidation, and conversions of N-containing groups accounted for reduced charge transfer resistance, leading to improvement of long-term performance. It is reasonable to believe that our work provides new strategy for enhancing CDI performance by using newly developed MCE