Nitrogen-Doped Graphite Felt on the Performance of Aqueous Quinone-Based Redox Flow Batteries
Modification of electrode is vitally important for achieving high energy efficiency aqueous quinone-based redox flow batteries (AQRFBs). The modification of graphite felt (GF) is carried out by means of urea hydrothermal reaction, and simultaneously the effect of hydrothermal reaction time on the functional groups and surface structure of nitrogen-doped graphite felt is studied. The surface morphology and defect, element content and surface chemical state of the modified electrode are characterized by scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), Raman, and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the modified electrodes is evaluated by cyclic voltammetry, electrochemical impedance spectra and single cell. These results indicate that specific surface area, hydrophilicity and conductivity of graphite felt have improved by nitrogen doping. The nitrogen-doped graphite felt (NGF) demonstrates an outstanding electrochemical catalytic activity and less charge transfer resistance. With the NGF, the battery exhibits 8.0% increase of energy efficiency of aqueous quinone redox flow batteries at 100 mA/cm2.