Degradation mechanism of Ti/IrO2(0.7) + MnO2(0.3) anode for oxygen evolution was studied in 0.5 M H2SO4 solution by field emission scanning electron microscopes (FESEM), Tafel slope, X-ray diffraction (XRD) and electrochemical impedance spectroscopic (EIS). The whole surface of the non-electrolyzed Ti/IrO2(0.7) + MnO2(0.3) anode consisted of nano-IrO2 poles array. The anode surface had hardly discovered cracks and had compact morphology that can prevent the electrolyte from entering the Ti/oxide interface and an insulating TiO2 film from growing on the Ti-based surface. An insulating TiO2 phase had not been generated on the Ti/oxide interface cluring the process of O-2 evolution and the inactive anode surface still remained mass of the IrO2 and MnO2 OXides.The chemical dissolution of Ti/IrO2(0.7) + MnO2(0.3) anode coating was not the main reason for electrode degradation in 0.5 M H2SO4 solution. The degradation mechanism of Ti/IrO2(0.7) + MnO2(0.3) anode differed from other conventional oxide electrodes for 02 evolution in acid medium. The platforms of Tafel slope and anode potential (900-1050 h) indicated that the change of the oxygen evolution reaction (OER) mechanism was the main reason for degradation of Ti/IrO2(0.7) + MnO2(0.3) anode due to the change of adsorption intermediate. (C) 2008 Elsevier Ltd. All rights reserved.