Porous Nb2O5 electrodes were fabricated by applying anodic pulses of 700 V and 10 ms duration to pure Nb in phosphate buffered saline solution (PBS), aiming at biomaterial applications. The porosity of the oxide could be controlled by the number of pulses. X-ray photoelectron spectroscopy analysis confirmed the oxide to be Nb2O5. The electrochemical behavior and interfacial properties of the porous Nb2O5 were characterized in PBS by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). EIS measurements indicate that the oxide film has a two-layer structure with a compact inner layer and a porous outer layer, and the pores were sealed by precipitates during long-time aging in PBS. The two-layer structure of the oxide film was observed by examination of the cross section using scanning electron microscopy in backscatter mode. The CV measurements reveal that the oxide exhibits an electrochemical "rectifying" property. It is stable over a wide potential range but shows hydrogen uptake upon cathodic polarization below -1 V vs Ag/AgCl. (c) 2006 The Electrochemical Society.