In situ simultaneous XAS and electrical characterizations of Pt-doped tin oxide thin film deposited by pyrosol method for gas sensors application

Pt-doped polycrystalline tin oxide thin films have been synthesized by a modified chemical vapor deposition process using the pyrolysis of an aerosol generated by ultrahigh frequency spraying of a volatile precursor solution. We have analyzed the role played in the sensing processes, by Platinum aggregates dispersed in SnO2 thin films used for the detection of various reducing gases such as CO or H2S. X-ray absorption spectroscopy (XAS) analysis has allowed us to follow in situ the evolution of the oxidation state of platinum aggregates. The effect of Pt nanoparticles on the CO and H2S sensitivity of SnO2 thin films was studied in real working conditions using X-ray absorption spectroscopy (XAS) and electrical conductivity measurement. Under CO and when they are incorporated in a very weak quantity (which correspond to a very small particles), platinum particles change in a reversible manner, their oxidation state, according to the nature of the atmosphere. Different situation has been observed in the presence of H2S gas. (c) 2006 Elsevier B.V. All rights reserved.