The reactive surface sites and the H2S sensing potential for the SnO2 produced by a mechanochemical milling

SnCl2 powder was milled with Ca(OH)(2) and K2CO3 powder respectively in a ball mill at room temperature and in an air atmosphere. Pure SnO2 was obtained by removal of the CaCl2 or KCl by-product by washing the powder. An initial composition of SnCl2, K2CO3, and Cr(NO3)(3).O9H(2)O was milled to produce the doped SnO2 phase with Cr on the surface. Heat-treatment results in the formation of a tetragonal phase. The infrared spectra for the different powders and from thick films of these materials are reported. An important finding is that during milling in the presence of water, OH groups are formed at the surface in great numbers. After heat-treatment at 400degreesC or higher, the OH bonds of adjacent grains are probably transformed into Sn-O-Sn bridges. Washing the material with pure ethanol, instead of water, can result in the reduction of intensity for the band at 1450 cm(-1) due to the presence of the bridge bonding Sn-O-Sn. On exposure to H2S and CO gas, the SnO2 film prepared from anhydrous powder, has higher sensitivity than the SnO2 film, prepared from hydrated powder. It is shown that the SnO2 produced by mechanochemical synthesis can be successfully applied to a H2S gas sensor. (C) 2003 The Electrochemical Society.