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H2 sensing properties of an anodically oxidized Nb2O5 film coupled with a noble metal electrode (M/Nb2O5, M:Au, Pt and Pd) have been investigated under various operating conditions. Among the sensors tested, the Nb2O5 film with a Pd electrode, which was prepared by anodic oxidation in an aqueous solution of 0.5 M H2SO4, showed the highest H2 response, and the logarithmic sensor current under a forward bias was proportional to the logarithmic H2 concentration. The current-voltage characteristics of the Pd/Nb2O5 sensor at 100°C apparently showed a typical rectifying function of a metal-semiconductor junction, which was formed between the Pd electrode and the Nb2O5 thin film, especially in H2 balanced with dry air. The H2 response property was improved when it was operated under a forward bias above 150°C. Furthermore, it was confirmed that even at 28°C the Pd/Nb2O5 could respond to H2 in dry air.