In situ diffuse reflectance infrared spectroscopy study of CO adsorption on SnO2

The surface interaction between differently prepared tin oxide samples and CO was studied by Diffuse Reflectance Infrared Fourier Transform (DRIFT)-sp ectroscopy at room temperature. As samples, commercial powders (Merck) and home-made powders obtained by a sol-gel preparation were used. Several band s corresponding to isolated and rooted OH groups, coordinated water and con densed water in two forms: ordered lavers of water molecules and water in t he liquid form, were found. Their appearance and intensity depended on the sample origin and storing conditions. Moreover, the spectra of all samples show bands corresponding to different hydrated protons (H3O+, H5O2+) and ca rbonate ions of different intensities. To get information about the interac tion between SnO2 powders and CO, in-situ measurements were conducted. We f ound that differently bound water and specific surface OH-groups react with CO and that surface carbonate ions dissociate because of acidic intermedia te products. As a result, different bands corresponding to physisorbed CO a ppear at approximately 2200 cm(-1), together with changes in the region cor responding to covalent bound chelating and bridging bidentate carbonates an d carboxylate (between 1700 and 1000 cm(-1)). (C) 2001 Elsevier Science B.V . All rights reserved.