Graphene/Nafion ink-impregnated graphite felt for both positive and negative sides of enhanced vanadium redox flow battery

Electrocatalysts have a key role in the reactions of vanadium redox flow batteries (VRFB). A practical immersion-drying method is used to decorate graphene on graphite felt electrodes. Cyclic voltammograms illustrate that graphene plays an effective role in the formation and stability of redox peaks. Also, voltammograms show the rate capability of modified felts is enhanced remarkably, further confirmed by reduced charge transfer resistance obtained from electrochemical impedance spectroscopy. The results of cycling in a homemade battery show that the discharge capacity in the first cycle for the modified sample and the bare sample is equal to 1154 and 1244 mAh, respectively. The discharge energy density for the modified sample in the first cycle is about 1.17 Wh L −1 more than that of the bare one. The power of the battery containing the modified sample is 3.76 W, which is 0.12 W more than that of the battery containing the bare one, which is a result of the higher voltage of the battery with modified electrodes. The cycling stability of the modified electrodes has improved the voltage and energy efficiency of the battery containing them by 3% compared to the bare sample. Graphene has made these improvements by providing more surface area for redox reactions, creating a conductive network, and adding electrocatalytic properties to the graphite felt. The presented simple, inexpensive, and scalable method for decorating graphene on graphite felt is suitable for both positive and negative electrodes and can enhance high-rate charging and discharging capabilities of vanadium batteries.