Enhanced Charge Transfer by the Conductive Network Induced by Point-to-Point Transport between the Current Collector and a Flow-Electrode in Flow-Electrode Capacitive Deionization

Flow-electrode capacitive deionization (FCDI) has a large potential for deionization and resource recovery. However, difficulties in charge transfer hinder the development of the technology. In this study, carbon black, an excellent conductive additive (CB) dispersed by activated carbon (AC) is loaded onto nickel foam to create a current collector, constructing the conductive network via point-to-point charge transfer between the collector and a flow electrode. Enhanced charge transfer results in superior desalination performance, with the apparent salt removal rate being 1.7 times that of graphite-based FCDI (GP-FCDI). Roughness analysis indicates that AC can significantly reduce the agglomeration of CB and increase the number of conductive sites. Electrochemical tests reveal that the constructed network exhibits low ion and charge transfer resistance. Notably, the new collector maintains a higher desalination rate at low concentration slurry, attributed to direct charging through the collector. Long-term experiments confirm the stability of the coating, demonstrating both a high desalination efficiency and consistent effluent quality. Charge efficiency keeps over 90% during 25000 s. The effluent conductivity remains stable at approximately 200 μS cm–1, significantly lower than GP-FCDI’s range of 737–1221 μS cm–1, showcasing superior performance.