Hydrogen sensing behavior of Pt-coated mesoporous anodic titania

We report on excellent hydrogen sensing properties of a Pt/TiO2 system based on mesoporous titania grown by plasma electrolytic oxidation of a Ti metal substrate. The Pt phase is deposited onto the titania surface as an electrically continuous Pt nanomesh layer with an e-beam process. Resistive sensor response between the Pt and Ti terminals of the resultant structure is studied at room temperature for different partial pressures of H2 gas (0.003-3 Torr) and different source voltages (0.5-2.0 V). A maximum resistance effect, reaching four orders of the magnitude for 3 Torr H2 in 160 Torr O2 is obtained at the bias voltage 1.4 V, and a strong effect is detected for only 0.003 Torr, or 20 ppm H2 concentration. For voltages in the range 1.0-1.4 V, electrical conductance of the sample is about a linear function of the H2 partial pressure in the gas phase. Influence of the background atmosphere (O2, N2 and vacuum) and the effect of bias reversal were investigated also, leading to a conclusion that the sensing mechanism can be related to ionic transport in the TiO2 layer.