H2 sensing performance of anodically oxidized TiO2 thin films equipped with Pd electrode

Hydrogen sensing properties of TiO2 thin films prepared by different methods and equipped with different kinds of metal electrodes have been tested. The most developed submicron-sized pore structure was found in the TiO2 thin film prepared by anodic oxidation of a Ti metal plate in a H2SO4 solution at 20 °C. The sensor fabricated with this film and a Pd electrode showed the highest H2 response among the sensors fabricated with different TiO2 films and electrode metals at elevated temperatures. This TiO2 thin film sensor equipped with a Pd electrode can be classified into a diode-type sensor from the change in I–V curve induced by H2, and is characterized with reversible H2 response even in N2 atmosphere. The H2 sensing mechanism is suggested to arise from dissolution of H atoms into the Pd electrode and a decrease in Schottky barrier height at the interface between the Pd electrode and the TiO2 thin film. Although the present sensor showed pretreatment-dependent H2 response properties, modification of the Pd electrode was found to be effective for reducing or improving the pretreatment-dependent H2 response properties.