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Tuning the photocatalytic of TiO2 based films by orientated growth and surfacefunctinalization
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
2014 (English)In: 5th International Symposium on Transparent Conductive Materials / [ed] G. Kiriakides, Mitos, Heraklion, Crete , 2014Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Anatase TiO2 is by far the most studied photocatalytic material.1 Normally anatase particlesare dominated by the low energy (101) surface planes with small fractions of (001) facets, whichgives the particles their characteristic truncated bi-pyramidal morphology. TiO2 thin films preparedby reactive DC magnetron sputtering in O2 atmosphere are initially amorphous, but after heattreatmentit has been reported that preferential alignment occurs for grains in the <004> direction,which is thought to expose reactive (001) planes at the film surface.2 Here, anatase TiO2 thin filmswere deposited by reactive DC magnetron sputtering in Ar/O2 atmosphere, and were characterizedusing Rietveld refined grazing-incidence XRD, AFM, spectrophotometry and surface profilometry.Upon heat-treatment for 1 h at 500ºC the as-deposited amorphous films crystallized in the anatasephase with grain size between 18 and 26 nm. By varying the partial O2 pressure in the depositionchamber, the degree of orientation of the grains in the film could be systematically varied withpreferred <001> orientation changing between 12 and 38%. Photocatalytic degradation ofmethylene blue dye was measured by in situ absorption spectroscopy in a home-built reactor.3 Aclear relation was found between the amount of preferred orientation and photocatalytic reactivityof the films. The rate increase is non-linear and follows approximately a square dependence on thedegree of <001> orientation.Moreover, we show that modifications of the acid–base properties of TiO2-basedphotocatalysts can be used to improve their sustained photocatalytic activity. Acid surfacefunctionalization was accomplished by a novel method, where SO2 gas molecules are adsorbed onsurface oxygen vacancy sites in a reactive atmosphere, and which subsequently are oxidized tosulphate groups.4 Here we have applied this method to DC magnetron sputtered films with variousdegree of <001> orientation, as well as on Doctor bladed TiO2 film from nanoparticle suspensions.In situ FTIR spectroscopy measurements of the photo-degradation of acetaldehyde shows thepresence of surface sulphate groups weakens bonding of intermediate aldehyde and carboxylatespecies to the surface, and lowers the formation rate of intermediate formate products. Repeatedadsorption/photo-oxidation cycles show that the acetaldehyde adsorption capacity is higher onsulphated TiO2 films, which can be explained by a reduced site-blocking effect of strongly bondedformate species which limit the complete oxidation on TiO2.The presented results point toward new strategies to purposefully improve the photocatalyticactivity of TiO2 films by industrially up-scalable technologies, and also show that appropriatemodification of the acid-base surface properties can help to avoid photocatalyst deactivation

Place, publisher, year, edition, pages
Mitos, Heraklion, Crete , 2014.
National Category
Engineering and Technology
Research subject
Chemistry with specialization in Physical Chemistry; Chemistry with specialization in Materials Chemistry; Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
URN: urn:nbn:se:uu:diva-238323OAI: oai:DiVA.org:uu-238323DiVA: diva2:770874
Conference
5th International Symposium on Transparent Conductive Materials, Crete, Greece, 12 - 17 Oct 2014
Funder
EU, FP7, Seventh Framework Programme, 267234
Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2014-12-16Bibliographically approved

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Österlund, Lars

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