Enabling a Large Accessible Surface Area of a Pore-Designed Hydrophilic Carbon Nanofiber Fabric for Ultrahigh Capacitive Deionization

Although porous carbons have been widely used for capacitive deionization, the low accessible surface area because of the hydrophobic microporous structure results in unsatisfied desalination capacity, which drastically hinders their practical application. Herein, a novel carbon nanofiber fabric with a large accessible surface area was prepared by electrospinning using the uniformly dispersed ferrocene as a pore former. The carbon nanofiber fabric with good mechanical strength and flexibility can be directly used as a filter membrane to filter simulated sandy seawater. The high content of heteroatoms increases the surface polarity of the carbon nanofiber, while the well-controlled interconnected mesoporous structure of the optimized sample facilitates fast transport and adsorption of hydrated Na⁺ and Cl^–. Thus, the hydrophilic carbon nanofiber fabric shows a Brunauer–Emmett–Teller surface area of 922 m² g^–1 and a large accessible surface area of 405 m² g^–1, leading to a high capacitance of 263 F g^–1 in the NaCl electrolyte. Most importantly, it shows an ultrahigh desalination capacity of 19.34 mg g^–1, which is much higher than most of the previously reported carbon materials. The high desalination capacity, fast adsorption rate, and good cycle stability make the as-prepared carbon nanofiber fabric an attractive candidate for practical application.