This paper reports a facile method to fabricate porous carbon nanofibers (PCNFs) via electrospinning polyacrylonitrile/dimethyl sulfone (PAN/DMSO 2 ) pristine fibers followed by preoxidation and carbonization. The nanopores were produced due to the removal of DMSO 2 during the preoxidation process of the nanofibers, without additional chemical or physical activation processes involved. The specific surface and pore density were tunable by varying the PAN/DMSO 2 ratio. The variation in the structure and composition of the nanofibers after heat treatment was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. As a free-standing electrode material in electrochemical capacitors, the PCNFs showed an enhanced electrical double layer capacitance characteristic, confirmed by cyclic voltammetry. The PCNFs were used successfully for capacitive deionization (CDI) with an enhanced desalination amount of 8.1 mg g À1 , 4.5 times higher than that of pure PAN-based CNFs. The good stability demonstrated that these porous carbon nanofibers could be deployed for CDI application.

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Activated carbon (AC) is one of the most typical carbon materials used for capacitive deionization (CDI) due to its large specific surface area and porous structure. However, the poor water wettability of AC remains a major challenge for CDI application in aqueous solutions. Here, polydopamine (PDA) is facilely modified on AC surface (PDA/AC) via self-polymerization of dopamine to improve its wettability, while the PDA thickness can be conveniently tuned by varying the soak time. X-ray photoelectron spectroscopy (XPS), Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), N2 adsorption and contact angle measurements are taken to characterize the properties of PDA/AC. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis indicate that PDA/AC electrodes exhibit an ideal electrochemical double layer capacitive behavior. The salt removal amount of 12 mg/g on PDA/AC with 4 h soaking is achieved during the desalination process, compared to 4.5 mg/g of AC electrode. The PDA/AC electrode is a very promising material for capacitive deionization.