| Autor: |
Diulus JT; School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, Oregon 97331, USA., Elzein R; School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, Oregon 97331, USA., Addou R; School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, Oregon 97331, USA., Herman GS; School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, Oregon 97331, USA. |
| Abstrakt: |
Tin dioxide (SnO 2 ) has various applications due to its unique surface and electronic properties. These properties are strongly influenced by Sn oxidation states and associated defect chemistries. Recently, the oxidation of volatile organic compounds (VOCs) into less harmful molecules has been demonstrated using SnO 2 catalysts. A common VOC, 2-propanol (isopropyl alcohol, IPA), has been used as a model compound to better understand SnO 2 reaction kinetics. We have used ambient-pressure x-ray photoelectron spectroscopy (AP-XPS) to characterize the surface chemistry of IPA and O 2 mixtures on stoichiometric, unreconstructed SnO 2 (110)-(1 × 1) surfaces. AP-XPS experiments were performed for IPA pressures ≤3 mbar, various IPA/O 2 ratios, and several reaction temperatures. These measurements allowed us to determine the chemical states of adsorbed species on SnO 2 (110)-(1 × 1) under numerous experimental conditions. We found that both the IPA/O 2 ratio and sample temperature strongly influence reaction chemistries. AP-XPS valence-band spectra indicate that the surface was partially reduced from Sn 4+ to Sn 2+ during reactions with IPA. In situ mass spectrometry and gas-phase AP-XPS results indicate that the main reaction product was acetone under these conditions. For O 2 and IPA mixtures, the reaction kinetics substantially increased and the surface remained solely Sn 4+ . We believe that O 2 replenished surface oxygen vacancies and that SnO 2 bridging and in-plane oxygen are likely the active oxygen species. Moreover, addition of O 2 to the reaction results in a reduction in formation of acetone and an increase in formation of CO 2 and H 2 O. Based on these studies, we have developed a reaction model that describes the catalytic oxidation of IPA on stoichiometric SnO 2 (110)-(1 × 1) surfaces. |
