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Article: The degradation mechanism of methyl orange under photo-catalysis of TiO 2
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TitleThe degradation mechanism of methyl orange under photo-catalysis of TiO 2
 
AuthorsYu, L1
Xi, J2
Li, MD1
Chan, HT1
Su, T1
Phillips, DL1
Chan, WK1
 
Issue Date2012
 
PublisherRoyal Society of Chemistry. The Journal's web site is located at http://www.rsc.org/pccp
 
CitationPhysical Chemistry Chemical Physics, 2012, v. 14 n. 10, p. 3589-3595 [How to Cite?]
DOI: http://dx.doi.org/10.1039/c2cp23226j
 
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.
 
ISSN1463-9076
2013 Impact Factor: 4.198
 
DOIhttp://dx.doi.org/10.1039/c2cp23226j
 
ReferencesReferences in Scopus
 
DC FieldValue
dc.contributor.authorYu, L
 
dc.contributor.authorXi, J
 
dc.contributor.authorLi, MD
 
dc.contributor.authorChan, HT
 
dc.contributor.authorSu, T
 
dc.contributor.authorPhillips, DL
 
dc.contributor.authorChan, WK
 
dc.date.accessioned2012-10-08T03:21:48Z
 
dc.date.available2012-10-08T03:21:48Z
 
dc.date.issued2012
 
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.
 
dc.description.naturelink_to_subscribed_fulltext
 
dc.identifier.citationPhysical Chemistry Chemical Physics, 2012, v. 14 n. 10, p. 3589-3595 [How to Cite?]
DOI: http://dx.doi.org/10.1039/c2cp23226j
 
dc.identifier.doihttp://dx.doi.org/10.1039/c2cp23226j
 
dc.identifier.epage3595
 
dc.identifier.hkuros199803
 
dc.identifier.issn1463-9076
2013 Impact Factor: 4.198
 
dc.identifier.issue10
 
dc.identifier.pmid22310904
 
dc.identifier.scopuseid_2-s2.0-84861559629
 
dc.identifier.spage3589
 
dc.identifier.urihttp://hdl.handle.net/10722/168630
 
dc.identifier.volume14
 
dc.languageeng
 
dc.publisherRoyal Society of Chemistry. The Journal's web site is located at http://www.rsc.org/pccp
 
dc.publisher.placeUnited Kingdom
 
dc.relation.ispartofPhysical Chemistry Chemical Physics
 
dc.relation.referencesReferences in Scopus
 
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 2
 
dc.typeArticle
 
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<contributor.author>Su, T</contributor.author>
<contributor.author>Phillips, DL</contributor.author>
<contributor.author>Chan, WK</contributor.author>
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<description.abstract>The 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 &#215; 10 -4 M, the degradation is mainly due to a direct hole oxidation process, while below 1.6 &#215; 10 -4 M, hydroxyl oxidation competes strongly and might exceed the hole oxidation. &#169; the Owner Societies 2012.</description.abstract>
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Author Affiliations
  1. The University of Hong Kong
  2. Tsinghua University