title: Effects of the SO4 groups on the textural properties and local order deformation of SnO2 rutile structure.
abstract: Sulfated tin oxide was synthesized from a hydroxylated tin oxide obtained by the precipitation method, followed by ion exchange of OH groups by SO4 species with a sulfuric acid solution. The samples were characterized by X-ray diffraction, transmission electron microscopy, thermoanalysis, and nitrogen physisorption by the Brunauer-Emmett-Teller method. The rutile crystalline structure was refined by the Rietveld method. Thermal analysis suggests the following stoichiometric formulas: SnO2-x(OH)2x and SnO2-x(OH)x(HSO4)x with X = 0.35 and 0.17 for non-sulfated and sulfated samples, respectively. The SO4 species remained strongly bonded at the SnO2 surface stabilizing its crystallite size against sintering, inhibiting the crystallite aggregation, and it acts as a structure porogen director mediating nanoparticle growth and assembly yielding a mesostructure form of SnO2 with wormhole morphology and high thermal stability. The interaction between SO4(2-) and the SnO2 surface changes the symmetry of the representative tin-oxygen octahedron. It relaxes the four tin-oxygen bond lengths located at the basal plane of the octahedron while the two apical Sn-O bonds decrease, producing a strong deformed octahedron, which could be transformed into a higher asymmetry in the electronic distribution around the Sn4+ nuclei. The elimination of SO4 groups brings about the coalescence and crystallite growth, which collapse the mesostructure form of SnO2, decreasing the surface area and porosity.
authors.affiliation: Instituto Mexicano del Petróleo, Prog. de Ingeniería Molecular, Eje Central Lázaro Cárdenas # 152, A.P. 07730 México, DF Mexico,
authors.forename: R
authors.initials: R
authors.lastname: Gutiérrez-Báez
authors.forename: J A
authors.initials: JA
authors.lastname: Toledo-Antonio
authors.forename: M A
authors.initials: MA
authors.lastname: Cortes-Jácome
authors.forename: P J
authors.initials: PJ
authors.lastname: Sebastian
authors.forename: A
authors.initials: A
authors.lastname: Vázquez