Structure and electrochemistry comparison of electrospun porous carbon nanofibers for capacitive deionization

The porous carbon nanofibers, PCNFPMMA and PCNFPS with different pore configuration, were prepared by electrospinning polyacrylonitrile (PAN) blending with the sacrificial polymers polystyrene (PS) and polymethyl methacrylate (PMMA) respectively, followed by carbonization. The pore structure and pore size of the obtained PCNFs can be tuned conveniently by altering the composition and content of the additives in the precursor solution. With PS as additive, the obtained PCNFPS consists mainly of non-interconnecting nanochannels along the fiber axis direction, with the specific surface area of 52.2 m2/g. While with PMMA as additive the obtained PCNFPMMA possessed interconnecting micro-mesoporous structure with the specific surface area of 393.4 m2/g. By using the porous carbon fibers as self-supporting electrode materials, the electrochemical double layer capacitance (EDLC) and impedance behavior were comparatively studied by cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS), respectively. The PCNFPMMA presents excellent EDLC characteristic and CDI desalination performance, owing to its interconnecting micro-mesoporous structure. But the non-interconnecting nanochannel configuration in PCNFPS is unfavorable for ionic transportation, resulting in a lower specific capacity and lower desalination capacitance. Under the optimal blend ratio of polymers, PCNFPMMA has a salt removal rate of 0.21 mg/g/min, much higher than that on PCNFPS (0.09 mg/g/min).