This study investigates the effects of platinum/carbon (Pt/C) catalysts on the performance of a vanadium redox flow battery. The Pt/C catalysts were synthesized using the impregnation-reduction method. The activity of these catalysts on the V(IV)/V(V) redox reaction was investigated using cyclic voltammetry, linear sweep voltammetry, and the rotating disk electrode (RDE) technique. The reaction rate constant K-0 and exchange current density i(0) were calculated from the RDE data. The K increased from 3.37 x 10(-6) cm . s(-1) to 6.86 x 10(-6) cm s(-1), and i(0) increased from 13.79 mu A. to 72.96 mu A as the Pt loading increased. Single-cell charge-discharge tests were performed with Pt/C on carbon felt as the positive electrode and raw carbon felt as the negative electrode. The energy efficiency of cells increased from 51.8% to 72.3% as the electrode material changed from carbon felt to Pt/C on carbon felt at a constant current density of 10 mA . cm(-2). The best Cell-D energy efficiency was 20.5% higher than that without an electrocatalyst (Cell-A). The Pt/C catalyst can also effectively reduce the cell internal resistance. The charge/discharge efficiency of a single cell with different anode catalyst is increased in the following order: Pt/C 15 wt% > Pt/C 10 wt% > Pt/C 5 wt% > carbon felt. (C) 2013 The Electrochemical Society. [DOI: 10.1149/2.073304jes] All rights reserved.