Iron nanoparticle embedded carbon nanofibers as flexible electrodes for selective chloride ions capture in capacitive deionization

Developing steady material for selective chloride ion capture is a challenging task to match the high capacity of counterparts during the practice of capacitive deionization (CDI). Iron-based materials have presented great potential for its environmentally friendly and low-cost features as chloride ion trapping electrodes. However, the severe capacity fading occurs due to the uncontrollable aggregation during cycling. Herein, iron nanoparticles embedded carbon fibers are creatively fabricated via an electrospinning technology followed by an anneal treatment. The presence of iron greatly increases the capacity of the electrode, while the coating structure of carbon nanofibers improves stability. Due to the synergistic effect of the electric double layer and the pseudocapacitance behavior, when employed as an anode for capacitive deionization device, this material shows an excellent adsorption capacity (82.5 mg g−1) and fast adsorption rate (20.4 mg g−1 min−1) during the desalting process. Meanwhile, the carbon-coated structure greatly prevents the dissolution or aggregation of iron nanoparticles in the reaction process, so that the electrode displays a splendid cycle stability and there is still a 93 % capacity retention rate after 30 cycles. In short, this work provides a new strategy for capacitive desalination of chloride ion trapping electrode with excellent performance by means of encapsulating iron nanoparticles into carbon nanofibers. •Iron nanoparticles embedded‑carbon nanofibers are fabricated as self-supporting electrode.•Highly dispersed iron nanoparticles rapidly trap chloride ions through redox reactions.•The armor structure inhibits the dissolution of iron nanoparticles and improves the cycle stability.