Study of Physical and Chemical Processes of H2 Sensing of Pt-Coated WO3 Nanowire Films

H-2 sensors able to operate at room temperature are very important for safe detection of H-2 leakage. We report the large electrical response to H-2 of Pt-coated WO3 (Pt-WO3) nanowire films without the need of using an external heater. More important, hydrogen sensing processes have been investigated under various conditions, including in air, vacuum filled with pure gas, and a mixture of H-2 and other gases. This is carried out with both electrical and optical methods. The evidence shows that hydrogen will inject into the nanowire and create oxygen vacancy, in addition to reducing adsorbed oxygen at the surface, as is often recognized. It is experimentally demonstrated that the increase of electrical conductivity resulting from the reaction with hydrogen is hampered by coadsorption of O-2, while N-2 has no such effect. A model has been developed to combine these new findings to give a clearer understanding of the mechanism responsible for H-2 sensing behavior.