Ultrahigh Salt Adsorption Capacity of Carbonaceous Electrode in a Rocking-Chair Capacitive Deionization through Surface Charge Modulation

Abstract

Addressing the challenges of ion adsorption capacity and electrode stability in capacitive deionization (CDI), this research introduces a pioneering anion exchange membrane (AEM)-based rocking chair CDI (RCDI) system equipped with activated carbon electrodes. Designed to counteract co-ion effects, this AEM-RCDI system significantly enhances ion-selective adsorption through improved electrode surface charge dynamics. This study also elucidates how these dynamics influence electrode potential distribution, the potential of zero charge, and the mechanism facilitating differential adsorption of ions, bridging fundamental electrochemical insight with practical improvement in desalination performance. Our investigation reveals that the oxidation of the carbon electrode, both during desalination and through targeted preoxidation, significantly boosts desalination efficacy and electrode stability. Especially, preoxidation increases cation adsorption, achieving an impressive desalination capacity of 87.3 mg g^–1, rate of 12 mg g^–1 min^–1, and charge efficiency of 88.6%, with remarkable stability over 240 desalination cycles. This study not only unveils key insights into the deionization mechanisms and properties of carbonaceous electrodes in RCDI but also sets a new benchmark for commercial CDI development.