Carbon Felt Coated with Titanium Dioxide/Carbon Black Composite as Negative Electrode for Vanadium Redox Flow Battery

Abstract

This investigation focuses on the effect of titanium dioxide (TiO2) coatings of a carbon black (XC-72) negative electrode on the performance of a vanadium redox flow battery (VRFB). TiO2, a hydrophilic material, was added to the carbon electrode to improve the wettability and reduce the electrical resistance of the electrode surface. The electrochemical performances of homemade TiO2, commercial TiO2, and carbon felt are investigated by using cyclic voltammetry and single-cell charge–discharge measurements. An electrode with 20 wt% of fabricated TiO2 loading at a scan rate of 0.006 V s−1 shows a specific capacitance (Cs,t) of 186.2 F g−1, which is 55.5% and 12.2% higher than that of pure carbon electrode (119.7 F g−1) and commercial TiO2 (166.0 F g−1), respectively. At current density of 200 mA cm−2, the energy storage efficiency (ηE = 65.4%) of the single cell with 20 wt% homemade TiO2/C-containing carbon felt negative electrode is 16.0% and 6.1% higher than that of the negative electrode with raw carbon felt (ηE = 56.4%) and of the negative electrode containing commercial TiO2/C (ηE = 61.6%), respectively. These results demonstrate the potential application of TiO2/C electrodes for high-efficiency VRFBs at high current densities.