Electrospun nitrogen-doped carbon nanofiber as negative electrode for vanadium redox flow battery

Carbon nanofiber (CNF) was developed via electrospinning technique with polyacrylonitrile as precursor. Nitrogen-doped carbon nanofiber (NCNF), synthesized by liquid phase dispersion and carbonization processes with urea at 800-1000 degrees C, were investigated as negative electrode for vanadium redox flow battery (VRFB). Morphology and structure of CNF and NCNF were systematically investigated by SEM, Raman, XPS, etc. The morphology of CNF is not changed by nitrogen doping. However, nitrogen doping can lead to marked enhancement of surface defect and hydrophilicity. Electrochemical test results show that NCNF treated at 900 degrees C (CNF-N9) exhibits the best electrochemical performance. The excellent energy storage performance of the cell is obtained by using CNF-N9. Discharge capacity of cell for CNF-N9 arrives at 98.0 mA h, 30.0 mA h higher than that of the pristine cell at 90 mA cm(-2). And energy efficiency of the cell using CNF-N9 increases by 6.3% compared with pristine cell. Outstanding performances of CNF-N9 come from the increase of surface defect and the improvement of hydrophilicity and conductivity resulting from nitrogen doping, further promoting the electron and mass transfer between vanadium ion and electrode.