Interactions of Sn2+ dopant ions located on surface sites of anatase-type TiO2 with adsorbed H2S molecules studied using 119Sn Mössbauer spectroscopic probe

Information provided by 119Sn2+ Mössbauer probe ions, located on surface sites of anatase-type TiO2 microcrystals exposed, at room temperature, to a H2S/H2 mixture, has permitted to conclude that the interaction of H2S molecules with the substrate surface leads to the dissociation of a fraction of the absorbate molecules. This gives rise to the formation of elemental sulfur which oxidizes the neighboring Sn2+ ions, the produced Sn4+ ions being found coordinated only by S2− anions. Subsequent exposure to ambient air is shown to result in the oxidation of S2− ions, yielding both S0 and SO42−-like species, with concomitant stabilization of Sn4+ ions in coordination polyhedra where they are surrounded by only oxygen anions.