Enhanced capacitive deionization of an integrated membrane electrode by thin layer spray-coating of ion exchange polymers on activated carbon electrode

Capacitive deionization (CDI) has emerged as a novel desalination technology due to its cleanliness and low energy consumption. Despite being based on the principle of an electric double layer for ion adsorption on porous carbon materials, the inevitable faradaic reaction and the existence of co-ion repulsion reduce the charge efficiency (CE), leading to a low salt adsorption capacity (SAC). Herein, an integrated membrane electrode (IME), prepared by spray-coating a thin layer of an ion exchange polymer on the activated carbon (AC) electrode, effectively improves the selectivity of the electrode to the counter-ion, resulting in a high CE and high SAC with good stability. The results show that the CE of CDI performed using IMEs is between 70% and 98% during multiple adsorption-desorption cycles, and the SAC is up to 14–20 mg g⁻¹, which is much higher than CE (35–65%) and SAC (7–13 mg g⁻¹) of traditional CDI with pristine AC electrodes. This study indicates that CDI using IMEs is advantageous for desalination with great application potential.