Poly(arylene alkylene)-Based Ion-Exchange Polymers for Enhancing Capacitive Desalination Capacity and Electrode Stability
Yingsheng Xu, Tao Jiang, Xinyuan Zhang, Guoxin Cao, Yang Lv, Haibing Wei, Hongjian Zhou
Abstract
Membrane capacitive deionization (MCDI) has emerged as a promising technique for desalination due to the merits of high capacity, low energy consumption, and high energy efficiency. However, normal free-standing ion-exchange membranes are used in MCDI, and they usually have the drawbacks of high thickness and cost, limiting their large-scale application in industrial promotion. Here, we report a scalable, continuous processing strategy to produce MCDI electrodes for enhancing capacitive desalination capacity and electrode stability, in which the carbon electrodes are coated using poly(arylene alkylene)-based ion-exchange polymers. The MCDI based on integrated ion-exchange polymer-coated membrane electrodes (C-MCDI) delivered a high salt adsorption capacity of up to 23.7 mg g –1 and an excellent charge efficiency of up to 98%, far higher than that of membrane-free CDI with bare carbon electrodes and MCDI with free-standing membrane-based carbon electrodes (FS-MCDI). The COMSOL simulation demonstrated that the coated ion-exchange membrane in C-MCDI was more effective for reducing the interface contact resistance between the carbon and ion-exchange membrane and enhancing the ion transportation. Furthermore, the C-MCDI device showed a long lifespan with a stable desalination capacity of around 18.6 mg g –1 after 500 cycles; instead, the capacity continuously attenuated to near zero in CDI with bare carbon electrodes. Hence, this work proposed two novel polymer-based ion-exchange materials for scalable fabrication of high-performance MCDI electrodes via an environmentally friendly, cost-effective, and process-integrated method.