Constructing ionic highway in capacitive deionization via integrated electrodes based on bifunctional ionomer

In this work, bifunctional ionomeric capacitive deionization (BICDI) electrode are constructed by using bifunctional ionomer as electrode binder and ion exchange material for the enhancement of desalination performance. Compared with traditional membrane capacitive deionization (MCDI) electrodes, the BICDI electrodes were fabricated by using the poly(arylene alkylene) based ionomer to substitute the PVDF binder and ion exchange membrane (IEM). The BICDI electrode based on bifunctional ionomer exhibits higher hydrophilicity, special ion exchange capability, as well as excellent electrochemical properties in comparsion with that of MCDI electrode counterpart. The built-in ionic groups in poly(arylene alkylene) based ionomers could create interconnected ionic highway between different electrode particles, which encourages effective ion transport. The desalination results validated that the salt adsorption capacity (SAC) of carbon-based BICDI electrodes reached 19.2 mg g−1, which is 2.2 times that of MCDI electrodes during adsorption-desorption cycles. Meanwhile, BICDI electrode possesses exceptional charge efficiency (96.6 %), which is much higher than that of MCDI (76.8 %). In the case of BICDI device, the ionomer utilization rate increased by a factor of 88 compared to that of ion exchange membrane in MCDI device. Especially, the economic cost of the integrated BICDI electrodes module is only $35 m−2, which is much cheaper than that in conventional MCDI system ($520 m−2). It is reasonable to believe that the integrated BICDI electrode incorporated with charged bifunctional ionomer proposed in this work provide novel insights and strategies for the high-performance and large-scale CDI applications.