Sulfur dioxide adsorption and photooxidation on isotopically-labeled titanium dioxide nanoparticle surfaces: roles of surface hydroxyl groups and adsorbed water in the formation and stability of adsorbed sulfite and sulfate

• DOI: 10.1039/c2cp23684b
• Publication Date: 2012-03-04T10:44:06Z
• Authors: Charith E. Nanaya...; John Pettibone; Vicki H. Grassian
• Keywords: Bisulfite; Titanium Dioxide

Transmission FTIR spectroscopy and X-ray photoelectron (XPS) are used to probe the details of sulfur dioxide adsorption photooxidation on titanium nanoparticle surfaces. Adsorption sites, surface speciation chemistry have been determined from analysis spectra in conjunction with isotope labeling experiments. These data show that hydroxyl groups involved dioxide, particularly, reacts either one O–H group yield adsorbed bisulfite or two sulfite water. Using 16O–H, 16O–D 18O–H labeled groups, additional insights into mechanism as well shifts vibrational modes determined. Upon irradiation, sulfite/bisulfite converts sulfate. The relative stability sulfate TiO2 surfaces was also examined presence increasing humidity (RH). It is shown here water can more easily displace compared by forming a stable complex differences RH-dependent species form result heterogeneous reactions oxide particles has important implications mineral dust aerosol atmosphere.