IrO2 thin films were prepared by radio frequency magnetron sputtering technique at different substrate temperatures. Supercapacitive properties of the films were studied by cyclic voltammetry and electrochemical impedance spectroscopy in 1 M LiNO3 electrolyte for the first time. The specific capacitance of the single IrO2 film electrode was calculated to be 293 F g(-1) at a scan rate of 5 mV s(-1) for the sample prepared at room temperature. After 1000 cycles, the specific capacitance of IrO2 electrode decreases slightly, indicating the sputtered IrO2 thin-film electrode has excellent cycling performance in aqueous LiNO3 electrolyte. (C) 2008 The Electrochemical Society.