A newly designed graphite-polyaniline composite current collector to enhance the performance of flow electrode capacitive deionization

Abstract

• A novel polyaniline-graphite composite current collector was developed for the FCDI. • FCDI with hybrid material current collector shows higher deionization performance. • PANI optimizes the charge transfer between the channel and electrode. • The smooth and hydrophilic channel alleviates flow electrode sediment. Flow-electrode capacitive deionization (FCDI) is an efficient and low-energy ions separation technology. However, the unsatisfactory conductive connection of the circuit in graphite (GP) channel and inevitable flow electrode (FE) sediment impedes the application of FCDI. Herein, a simple electrochemical polymerization method was adopted to build a polyaniline-graphite (PGP) composite current collector. The average salt removal rate (ASRR) of PGP-FCDI was increased by 1.46 times than GP-FCDI. The ohmic resistance of PGP-FCDI was found to be 3.5 Ω, which is much lower than that of GP-FCDI (12.9 Ω). The high conductive capacity of polyaniline provides excess conductive sites, which contributes to enhanced charge transfer efficiency. Furthermore, the composite material changes the polarity of the graphite surface and destroys the electrostatic interaction between graphite and activated carbon. As a result, electrode sediment is reduced by 15%. In addition, the performance of PGP-FCDI remains stable after continuous deionization cycles. The new features significantly contribute to the improved deionization performance and long-term stability of FCDI.