This study investigates the effects of adding titanium dioxide (TiO2) particles to the negative electrode of a vanadium redox flow battery (VRFB) on the battery's performance. Results show that TiO2 addition changes the wettability and electrical resistance of the electrode surface. The water contact angle on the electrode surface decreases with increased weight percentage of TiO2 particles in the electrode. The electrochemical performance of these electrodes with different loading amounts is studied by cyclic voltammetry and single-cell charge-discharge measurements. Adding an adequate amount of TiO2 particles to the carbon electrode promotes the electrode specific capacitance and charge-discharge efficiency of a single cell. An electrode with 20 wt% TiO2 loading at a scan rate of 0.04 V s(-1) shows a high specific capacitance (C-s,C- t) of 156.2 F g(-1), which is 59.1% higher than that of pure carbon electrode (98.2 F g(-1)). Similarly, the energy storage efficiency (eta(E) = 72.5%) of a single TiO2/C cell with 20 wt% modified carbon felt is 30.4% higher than that of a cell with raw carbon felt (eta(E) = 55.6%). Thus, the TiO2/C electrode increases the cell energy storage efficiency. These results demonstrate the potential application of TiO2/C electrode in VRFBs. (C) 2013 The Electrochemical Society.