A single-electrode evaluation method used for analyzing the working mechanism and capability of integrated membrane capacitive deionization

Abstract

The evaluation of capacitive deionization (CDI) often relies on indicators like salt adsorption capacity and rate. However, these indicators encompass the entire system, including the anode and cathode. In practice scenarios, differences in specific capacitance, weight, and potential of zero charge result in varying theoretical ion adsorption capacity (IAC) and electrode potential. Hence, it is crucial to assess the deionization performance of individual electrodes. In this study, by introducing a reference electrode into the desalination device and enhancing the effective area and mass loading of the counter electrode, a single-electrode evaluation device was established to specifically analyze the deionization performance of the working electrode. Through this evaluation method, the single-electrode deionization performances of the anodic and cathodic integrated membrane electrodes (IMEs) were investigated, respectively, shedding light on the impact of IME on the Faradaic side reactions and co-ion effect. The results indicate that IME maintains an effective working voltage window and improves its stability. The cathodic IME effectively curbs the transport of dissolved oxygen, and the anodic IME prevents the carbon oxidation, thereby bolstering their IACs. This research not only elucidates the operational mechanism of IME but also highlights the feasibility of the single-electrode evaluation strategy in appraising asymmetric CDI.