A novel graphite felt electrode modified with tungsten trioxide (WO3) was developed to improve the electrochemical performance of graphite felt toward the VO2+/VO2+ redox pair. WO3 was prepared using a hydrothermal method, and the morphology of WO3 structures was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical property of WO3-modified graphite felt toward VO2+/VO2+ was carefully characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The hydrogen-vanadium redox flow battery (H-VRFB) test indicates that single cells using 1.1 mg cm(-2) WO3-modified graphite felt exhibited excellent performance at 70 mA cm(-2), and the corresponding coulombic, voltage, and energy efficiencies were 99.1%, 88.66% and 87.86%, respectively. (C) 2014 Elsevier Ltd. All rights reserved.