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- Hagglund, C, et al.
(författare)
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In situ reactivity and FTIR study of the wet and dry photooxidation of propane on anatase TiO2
- 2005
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 109:21, s. 10886-10895
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Tidskriftsartikel (refereegranskat)abstract
- The photocatalytic oxidation (PCO) of trace amounts of propane (500 ppm) on nanocrystalline anatase TiO2 has been investigated in situ as a function of temperature (T = 318-473 K), humidity (C-H2O = 0-4%), and time by means of mass spectrometry and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Propane adsorbs associatively on TiO2 at 318 K in dry air, while at 473 K small amounts of thermal dissociation products appear on the surface. In agreement with previous studies, propane is found primarily to be converted to acetone by reactions with photogenerated oxygen radicals. Various successive reaction paths exist, where the branching depends on the temperature and hydroxylation state of the surface. Under dry conditions at 318 K, acetone oxidation is initially kinetically hindered, while, above 400 K, acetone readily decomposes. The thermally assisted reaction channel leads to detrimental bonding of surface species and inhibition of the catalytic activity. It is manifested by a coloration of the sample and suggested to be coupled to surface reduction. Under humidified conditions, there is an optimum of the PCO in C-H2O and T space, which is estimated to correspond to an equilibrium coverage of one monolayer of H2O (or bilayer). The latter reaction condition also corresponds to sustained high propane conversion and is characterized by rapid establishment of steady state rates. The optimum PCO is discussed in terms of a balance between (i) sustaining enough of a photoactive water monolayer to avoid detrimental bonding of surface species, (ii) allowing reactants to adsorb and access bulk TiO2 photoexcitations, and at the same time (iii) maximizing the thermally assisted decomposition of intermediates.
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- Seidel, Y. E., et al.
(författare)
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Stability of nanostructured Pt/glassy carbon electrodes prepared by colloidal lithography
- 2008
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 155:3, s. K50-K58
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Tidskriftsartikel (refereegranskat)abstract
- The stability of nanostructured Pt/glassy carbon (GC) model electrodes upon exposure to a realistic electrochemical/electrocatalytic reaction environment (continuous reaction, continuous electrolyte flow) was studied by microscopic techniques, X-ray photoelectron spectroscopy, and electrochemical measurements. The model electrodes consist of Pt nanostructures with well-defined sizes and regular spacing on planar GC substrates, and were fabricated using colloidal lithography techniques. Additional plasma treatments of the GC substrates prior to Pt deposition were tested to improve the stability of the resulting Pt/GC model electrodes. Both evaporation and sputter deposition were used for Pt-film fabrication. The model catalysts prepared by Pt evaporation were found to be rather unstable. The stability was significantly improved for sputter-deposited Pt films, and Pt sputter deposition on a GC substrate, pretreated first in oxygen plasma and then in Ar plasma, resulted in stable model electrodes with a fully intact layer of Pt nanostructures after the electrocatalytic experiments.
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- Österlund, Lars, 1967-, et al.
(författare)
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Lithographic Techniques in Nanocatalysis
- 2007
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Ingår i: NANOCATALYSIS. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540326458 ; , s. 269-341
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Bokkapitel (refereegranskat)
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