Sinteza, karakterizacija i primena nedopiranih i dopiranih nanostrukturnih fotokatalizatora na bazi titan(IV)-oksida
Synthesis, characterization and application of undoped and doped nanostructured photocatalysts based on titanium(IV) oxide
Author
Đokić, Veljko
Mentor
Janaćković, Đorđe
Committee members
Petrović, Rada
Mijin, Dušan

Marinković, Aleksandar

Dramićanin, Miroslav

Metadata
Show full item recordAbstract
Titan(IV)-oksid (TiO2) je zbog svoje fotokatalitičke aktivnosti, hemijske i
biološke inertnosti, otpornosti na fotoindukovanu i hemijsku koroziju, netoksičnosti i
relativno niske cene, jedan od najčešće proučavanih poluprovodničkih materijala za
primenu u dekontaminaciji životne sredine, samo-čišćenju, uklanjanju mirisa,
sterilizaciji i obnovljivim izvorima energije. Zbog široke zabranjene zone i velike brzine
rekombinacije fotogenerisanih parova elektron-šupljina, efikasnost fotokatalizatora na
bazi TiO2 je i dalje mala za potencijalnu praktičnu primenu.
U poslednje četiri decenije veliki napor je uložen u istraživanja vezana za
poboljšanje fotokatalitičke efikasnosti TiO2 i njegovu moguću praktičnu primenu.
Generalno, fotokatalitička efikasnost TiO2 se može povećati: (1) smanjenjem energije
zabranjene zone dopiranjem i/ili proširenjem apsorpcije (u vidljivu oblast) upotrebom
fotosenzitizera, (2) poboljšanjem razdvajanja (smanjenjem brzine rekombinacije)
fotogenerisanih nosilaca naele...ktrisanja (elektron/šupljina) i (3) povećanjem specifične
površine i kvaliteta aktivnih mesta (za adsorpciju polutanata koje je potrebno
fotokatalitički razgraditi).
Cilj ove doktorske disertacije je proučavanje procesa formiranja nedopiranih i
dopiranih nanostrukturnih prahova i tankih filmova titan(IV)-oksida znatno poboljšane
fotokatalitičke efikasnosti. Da bi se postigla visoka fotokatalitička aktivnost u vidljivoj
oblasti, neophodno je generisati aktivne apsorpcione centre za vidljivu svetlost.
Pokazalo se da dopiranje anjonima nemetala predstavlja veliki potencijal u indukovanju
takve apsorpcije i dosta napora se ulaže u razvijanje metoda za sintezu anjon-dopiranih
TiO2 fotokatalizatora sa visokom aktivnošću u vidljivom delu spektra. Prema tome, u
ovoj doktorskoj disertaciji prvo je predstavljeno dobijanje TiO2 filmova pulsnom
laserskom depozicijom na staklenim supstratima u atmosferi kiseonika, metana, azota i
mešavini kiseonika i azota. Inkorporacija azota u rešetku TiO2 je uspešno ostvarena, što
je i pokazano merenjem optičke apsorpcije i fotoelektronske spektroskopije X-zracima
(XPS). Apsorpciona ivica N-dopiranih TiO2 filmova pokazuje crveni pomeraj do ~480
nm u odnosu na 360 nm u slučaju nedopiranih filmova. Fotokatalitička aktivnost TiO2
filmova ispitivana je u reakciji fotoredukcije toksičnih Cr(VI) u Cr(III) jone u vodenoj
sredini uz ozračivanje vidljivom i UV svetlošću. Najveću fotokatalitičku aktivnost u
prisustvu vidljive svetlosti pokazuju TiO2 filmovi deponovani u atmosferi azota, dok su
u prisustvu UV svetlosti najbolji rezultati dobijeni za TiO2 filmove deponovane u
atmosferi čistog metana i kiseonika...
Titania (TiO2) due to its photocatalytic activity, chemical and biological
inertness, resistance to chemical- and photo-corrosion, non-toxicity, and relatively low
cost, is one of the most studied semiconductors for environmental protection, selfcleaning,
deodorizing, sterilizing and renewable energy sources. Owing to its wide band
gap and high speed of electron/hole recombination, the efficiency of photocatalysts
based on TiO2 is however small for potential practical applications.
In the last four decades, much effort has been invested in research related to
improving the photocatalytic efficiency of TiO2 and its possible practical applications.
Generally, the photocatalytic efficiency of TiO2 can be increased by: (1) reducing the
band gap energy by doping and/or enlargement of its absorption in the visible region
using photosensitizes, (2) improving the separation (reducing the recombination rate) of
photogenerated charge carriers (electron/hole) and (3) increasing the specific surfa...ce
area and the quality of the active sites (for adsorption of pollutants to be
photocatalytically degraded).
The aim of this doctoral dissertation was the study of the process of the
formation of undoped and doped nanostructured powders and thin films of titanium(IV)
oxide with significantly enhanced photocatalytic efficiency. To this end, in order to
obtain high photocatalytic activity in the visible light region, it was therefore mandatory
to generate active visible light absorption centers. Anion doping proved itself to process
great potential in inducing such absorption, and intensive efforts have been directed
towards the development of methods for synthesizing anion-doped titania-based
photocatalysts with a large visible light response. Therefore, in this doctoral thesis, first
pulsed laser deposition of TiO2 films on glass substrates under oxygen, methane,
nitrogen and mixture of oxygen and nitrogen atmospheres is presented. Nitrogen
incorporation into the TiO2 lattice was successfully achieved, as demonstrated by
optical absorption and XPS measurements. The absorption edge of the N-doped TiO2
films was red-shifted by ≈480 nm from the undoped value of 360 nm. The
photocatalytic activity of TiO2 films was investigated during toxic Cr(VI) ions
photoreduction to the Cr(III) state in aqueous media under irradiation with visible and
UV light. Under visible light irradiation, the TiO2 films deposited under a nitrogen
atmosphere showed the highest photocatalytic activity, whereas on UV light exposure,
the best results were obtained for the TiO2 structures deposited under a pure methane or
oxygen atmosphere...