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Photocatalytic TiO2 thin films for air cleaning : Effect of facet orientation, chemical functionalization, and reaction conditions

Stefanov, Bozhidar, 1988- (författare)
Uppsala universitet,Fasta tillståndets fysik
Österlund, Lars, Prof (preses)
Uppsala universitet,Fasta tillståndets fysik
Niklasson, Gunnar, Prof (preses)
Uppsala universitet,Fasta tillståndets fysik
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Granqvist, Claes-Göran, Prof (preses)
Uppsala universitet,Fasta tillståndets fysik
Vesborg, Peter Christian Kjærgaard (opponent)
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 (creator_code:org_t)
ISBN 9789155493875
Uppsala : Acta Universitatis Upsaliensis, 2015
Engelska 148 s.
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)
Abstract Ämnesord
Stäng  
  • Poor indoor air quality is a source of adverse health effects. TiO2 coatings deposited on well-illuminated surfaces, such as window panes, can be used to fully mineralize indoor air pollutants by photocatalysis. In such applications it is important to ensure stable photocatalytic activity for a wide range of operating conditions, such as relative humidity and temperature, and to avoid deactivation of the catalyst.In this thesis photocatalytic removal of the indoor-pollutant acetaldehyde (CH3CHO) on nanostructured TiO2 films is investigated, and in particular it is proposed how such films can be modified and operated for maximum performance. Catalyst deactivation can be reduced by purposefully changing the surface acidity of TiO2 by covalently attaching SO4 to the surface. Moreover, the overall photocatalytic activity on anatase TiO2 films can be improved by increasing the fraction of exposed reactive {001} surfaces, which otherwise are dominated by {101} surfaces.In the first part of the thesis mode-resolved in-situ FTIR is used to elucidate the reaction kinetics of CH3CHO adsorption and photo-oxidation on the TiO2 and SO4 – modified TiO2 surfaces. Surface concentrations of main products and corresponding reaction rates were determined. Formate is the major reaction product, whose further oxidation limits the complete oxidation to gaseous species, and is responsible for photocatalyst deactivation by site inhibition. The oxidation reaction is characterized by two reaction pathways, which are associated with two types of surface reaction sites. On the sulfate modified TiO2 catalyst fewer intermediates are accumulated, and this catalyst resists deactivation much better than pure TiO2. A hitherto unknown intermediate – surface-bound acetaldehyde dimer with an adsorption band at 1643 cm−1 was discovered, using interplay between FTIR spectroscopy and DFT calculations.The second part of the thesis treats the effect of increasing the relative abundance of exposed {001} facets on the photocatalytic activity of anatase TiO2 films prepared by DC magnetron sputtering. A positive effect was observed both for liquid-phase photo-oxidation of methylene blue, and for gas-phase photocatalytic removal of CH3CHO. In both cases it was found that the exposed {001} surfaces were an order of magnitude more reactive, compared to the {101} ones. Furthermore, it was found that the reactive films were more resilient towards deactivation, and exhibited almost unchanged activity under varying reaction conditions. Finally, a synergetic effect of SO4 – modification and high fraction of exposed {001} surfaces was found, yielding photocatalysts with sustained high activity.The results presented here for facet controlled and chemically modified TiO2 films are of interest for applications in the built environment for indoor air purification and as self-cleaning surfaces.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik (hsv//swe)
ENGINEERING AND TECHNOLOGY  -- Chemical Engineering (hsv//eng)
TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)
ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)
TEKNIK OCH TEKNOLOGIER  -- Nanoteknik (hsv//swe)
ENGINEERING AND TECHNOLOGY  -- Nano-technology (hsv//eng)
NATURVETENSKAP  -- Kemi -- Teoretisk kemi (hsv//swe)
NATURAL SCIENCES  -- Chemical Sciences -- Theoretical Chemistry (hsv//eng)
NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)
NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Nyckelord

titanium dioxide
photocatalysis
thin films
surface functionallization
acetaldehyde
indoor air cleaning
sputter deposition
crystallographic modifications
preferential orientation
self-cleaning surfaces
Teknisk fysik med inriktning mot fasta tillståndets fysik
Engineering Science with specialization in Solid State Physics

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Av författaren/redakt...
Stefanov, Bozhid ...
Österlund, Lars, ...
Niklasson, Gunna ...
Granqvist, Claes ...
Vesborg, Peter C ...
Om ämnet
TEKNIK OCH TEKNOLOGIER
TEKNIK OCH TEKNO ...
och Kemiteknik
TEKNIK OCH TEKNOLOGIER
TEKNIK OCH TEKNO ...
och Materialteknik
TEKNIK OCH TEKNOLOGIER
TEKNIK OCH TEKNO ...
och Nanoteknik
NATURVETENSKAP
NATURVETENSKAP
och Kemi
och Teoretisk kemi
NATURVETENSKAP
NATURVETENSKAP
och Kemi
och Oorganisk kemi
Av lärosätet
Uppsala universitet

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