High H2 sensing performance of anodically oxidized TiO2 film contacted with Pd

TiO2 films with nanoholes have been prepared by anodic oxidation of a Ti plate in a H2SO4 solution. The TiO2 film sensor equipped with Pd and Ti electrodes exhibited a diode-type current–voltage characteristic in air, but nearly ohmic behavior in H2 balanced with dry air. The sensor showed quick response to H2 in dry air with high sensitivity, especially at 250 °C under a reverse bias voltage of 0.1 V. Reversible response to H2 was also achieved in N2, while the sensitivity decreased from that in air. The high H2 sensitivity in air is suggested to arise partly from the change in the height of the Schottky barrier at the interface between Pd and TiO2, and H atoms formed by dissociative adsorption of H2 at the Pd surface are assumed to play an important role in the H2 sensing properties. The sensor was less sensitive to CO, but water vapor interfered with the H2 sensitivity.