Infrared study of the adsorption of hexafluoroacetone on to rutile

Abstract

Infrared spectra have been recorded of hexafluoroacetone adsorbed on four samples of rutile which differed in their extents of dehydration by thermal activation or of reduction in hydrogen. Physically adsorbed hexafluoroacetone molecules interacted as hydrogen bond acceptors with surface hydroxyl groups, as electron donors with Ti⁴⁺ ions, and as electron acceptors with Ti³⁺ ions. Chemisorptive interactions involving surface hydroxyl groups or O^2– ions led to the formation of trifluoroacetate ions and precursor species resembling salts of hexafluoropropan-2,2-diol. In general, reduction of rutile in hydrogen weakened adsorptive interactions involving H-bond donation or electron acceptance by the oxide surface. In contrast interactions involving electron donation or nucleophilic attack of hexafluoroacetone by hydroxyl groups or O^2– ions were enhanced by reduction of the oxide in hydrogen.