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Article: The degradation mechanism of methyl orange under photo-catalysis of TiO 2

TitleThe degradation mechanism of methyl orange under photo-catalysis of TiO 2
Authors
Issue Date2012
PublisherRoyal Society of Chemistry. The Journal's web site is located at http://www.rsc.org/pccp
Citation
Physical Chemistry Chemical Physics, 2012, v. 14 n. 10, p. 3589-3595 How to Cite?
AbstractThe properties of photo-generated reactive species, holes and electrons in bulk TiO 2 (anatase) film and nano-sized TiO 2 were studied and their effects towards decomposing pollutant dye methyl orange (MO) were compared by transient absorption spectroscopies. The recombination of holes and electrons in nano-sized TiO 2 was found to be on the microsecond time scale consistent with previous reports in the literature. However, in bulk TiO 2 film, the holes and electrons were found to be on the order of picoseconds due to ultra fast free electrons. The time-correlated single-photon counting (TCSPC) technique combined with confocal fluorescence microscopy revealed that the fluorescence intensity of MO is at first enhanced noticeably by TiO 2 under UV excitation and soon afterwards weakened dramatically, with the lifetime prolonged. Photo-generated holes in nano-sized TiO 2 can directly oxidize MO on the time scale of nanoseconds, while free electrons photo-generated in bulk TiO 2 film can directly inject into MO on the order of picoseconds. Through cyclic voltammetry measurements, it was found that MO can be reduced at -0.28 V and oxidized at 1.4 V (vs. SCE) and this provides thermodynamic evidence for MO to be degraded by electrons and holes in TiO 2. Through comparison of the hole-scavenging effect of MO and water, it was found that in polluted water when MO is above 1.6 × 10 -4 M, the degradation is mainly due to a direct hole oxidation process, while below 1.6 × 10 -4 M, hydroxyl oxidation competes strongly and might exceed the hole oxidation. © the Owner Societies 2012.
Persistent Identifierhttp://hdl.handle.net/10722/168630
ISSN
2015 Impact Factor: 4.449
2015 SCImago Journal Rankings: 1.836
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorYu, Len_US
dc.contributor.authorXi, Jen_US
dc.contributor.authorLi, MDen_US
dc.contributor.authorChan, HTen_US
dc.contributor.authorSu, Ten_US
dc.contributor.authorPhillips, DLen_US
dc.contributor.authorChan, WKen_US
dc.date.accessioned2012-10-08T03:21:48Z-
dc.date.available2012-10-08T03:21:48Z-
dc.date.issued2012en_US
dc.identifier.citationPhysical Chemistry Chemical Physics, 2012, v. 14 n. 10, p. 3589-3595en_US
dc.identifier.issn1463-9076en_US
dc.identifier.urihttp://hdl.handle.net/10722/168630-
dc.description.abstractThe properties of photo-generated reactive species, holes and electrons in bulk TiO 2 (anatase) film and nano-sized TiO 2 were studied and their effects towards decomposing pollutant dye methyl orange (MO) were compared by transient absorption spectroscopies. The recombination of holes and electrons in nano-sized TiO 2 was found to be on the microsecond time scale consistent with previous reports in the literature. However, in bulk TiO 2 film, the holes and electrons were found to be on the order of picoseconds due to ultra fast free electrons. The time-correlated single-photon counting (TCSPC) technique combined with confocal fluorescence microscopy revealed that the fluorescence intensity of MO is at first enhanced noticeably by TiO 2 under UV excitation and soon afterwards weakened dramatically, with the lifetime prolonged. Photo-generated holes in nano-sized TiO 2 can directly oxidize MO on the time scale of nanoseconds, while free electrons photo-generated in bulk TiO 2 film can directly inject into MO on the order of picoseconds. Through cyclic voltammetry measurements, it was found that MO can be reduced at -0.28 V and oxidized at 1.4 V (vs. SCE) and this provides thermodynamic evidence for MO to be degraded by electrons and holes in TiO 2. Through comparison of the hole-scavenging effect of MO and water, it was found that in polluted water when MO is above 1.6 × 10 -4 M, the degradation is mainly due to a direct hole oxidation process, while below 1.6 × 10 -4 M, hydroxyl oxidation competes strongly and might exceed the hole oxidation. © the Owner Societies 2012.en_US
dc.languageengen_US
dc.publisherRoyal Society of Chemistry. The Journal's web site is located at http://www.rsc.org/pccpen_US
dc.relation.ispartofPhysical Chemistry Chemical Physicsen_US
dc.subject.meshAzo Compounds - chemistry-
dc.subject.meshCatalysis-
dc.subject.meshElectrochemistry-
dc.subject.meshPhotochemical Processes-
dc.subject.meshTitanium - chemistry-
dc.titleThe degradation mechanism of methyl orange under photo-catalysis of TiO 2en_US
dc.typeArticleen_US
dc.identifier.emailPhillips, DL:phillips@hku.hken_US
dc.identifier.emailChan, WK:waichan@hku.hken_US
dc.identifier.authorityPhillips, DL=rp00770en_US
dc.identifier.authorityChan, WK=rp00667en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1039/c2cp23226jen_US
dc.identifier.pmid22310904-
dc.identifier.scopuseid_2-s2.0-84861559629en_US
dc.identifier.hkuros199803-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-84861559629&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume14en_US
dc.identifier.issue10en_US
dc.identifier.spage3589en_US
dc.identifier.epage3595en_US
dc.identifier.isiWOS:000300314100038-
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridYu, L=7404163869en_US
dc.identifier.scopusauthoridXi, J=8567668500en_US
dc.identifier.scopusauthoridLi, MD=35173063700en_US
dc.identifier.scopusauthoridChan, HT=55232512300en_US
dc.identifier.scopusauthoridSu, T=55232687800en_US
dc.identifier.scopusauthoridPhillips, DL=7404519365en_US
dc.identifier.scopusauthoridChan, WK=13310083000en_US

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