Effect of electron acceptors H2O2 and O2 on the generated reactive oxygen species 1O2 and OH in TiO2-catalyzed photocatalytic oxidation of glycerol

Article abstract of DOI:10.1016/S1872-2067(16)62519-6

The effect of the electron acceptors H₂O₂ and O₂ on the type of generated reactive oxygen species (ROS), and glycerol conversion and product distribution in the TiO₂-catalyzed photocatalytic oxidation of glycerol was studied at ambient conditions. In the absence of an electron acceptor, only HO radicals were generated by irradiated UV light and TiO₂. However, in the presence of the two electron acceptors, both HO radical and ¹O₂ were produced by irradiated UV light and TiO₂ in different concentrations that depended on the concentration of the electron acceptor. The use of H₂O₂ as an electron acceptor enhanced glycerol conversion more than O₂. The type of generated value-added compounds depended on the concentration of the generated ROS.

Full text of DOI:10.1016/S1872-2067(16)62519-6

ChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1975–1981
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
ꢀ
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
ꢀ
ꢀ
Article
EffectꢀofꢀelectronꢀacceptorsꢀH
2
O
2
ꢀandꢀO
2
ꢀonꢀtheꢀgeneratedꢀreactiveꢀ

1
2
oxygenꢀspeciesꢀ O ꢀandꢀOH ꢀinꢀTiO
2
‐catalyzedꢀphotocatalyticꢀ ꢀ
oxidationꢀofꢀglycerolꢀ
ꢀa
ꢀb
ꢀc
ꢀa,d,
TrinꢀJedsukontorn ,ꢀVissanuꢀMeeyoo ,ꢀNagahiroꢀSaito ,ꢀMaliꢀHunsom *
ꢀ
aꢀFuelsꢀResearchꢀCenter,ꢀDepartmentꢀofꢀChemicalꢀTechnology,ꢀFacultyꢀofꢀScience,ꢀChulalongkornꢀUniversity,ꢀBangkokꢀ10330,ꢀThailandꢀ
bꢀCentreꢀforꢀAdvancedꢀMaterialsꢀandꢀEnvironmentalꢀResearch,ꢀMahanakornꢀUniversityꢀofꢀTechnology,ꢀBangkokꢀ10530,ꢀThailandꢀ
cꢀGraduateꢀSchoolꢀofꢀEngineeringꢀ&ꢀGreenꢀMobilityꢀCollaborativeꢀResearchꢀCenter,ꢀNagoyaꢀUniversity,ꢀNagoya,ꢀJapanꢀ
dꢀCenterꢀofꢀExcellenceꢀonꢀPetrochemicalꢀandꢀMaterialsꢀTechnologyꢀ(PETRO‐MAT),ꢀChulalongkornꢀUniversity,ꢀBangkokꢀ10330,ꢀThailandꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
TheꢀeffectꢀofꢀtheꢀelectronꢀacceptorsꢀH
2
O
2
ꢀandꢀO ꢀonꢀtheꢀtypeꢀofꢀgeneratedꢀreactiveꢀoxygenꢀspeciesꢀ
2
Receivedꢀ1ꢀJuneꢀ2016ꢀ
Acceptedꢀ18ꢀJulyꢀ2016ꢀ
Publishedꢀ5ꢀNovemberꢀ2016ꢀ
(ROS),ꢀandꢀglycerolꢀconversionꢀandꢀproductꢀdistributionꢀinꢀtheꢀTiO
2
‐catalyzedꢀphotocatalyticꢀoxida‐

tionꢀofꢀglycerolꢀwasꢀstudiedꢀatꢀambientꢀconditions.ꢀInꢀtheꢀabsenceꢀofꢀanꢀelectronꢀacceptor,ꢀonlyꢀHO
radicalsꢀwereꢀgeneratedꢀbyꢀirradiatedꢀUVꢀlightꢀandꢀTiO
2
.ꢀHowever,ꢀinꢀtheꢀpresenceꢀofꢀtheꢀtwoꢀelec‐
ꢀwereꢀproducedꢀbyꢀirradiatedꢀUVꢀlightꢀandꢀTiO ꢀinꢀdifferentꢀ
concentrationsꢀthatꢀdependedꢀonꢀtheꢀconcentrationꢀofꢀtheꢀelectronꢀacceptor.ꢀTheꢀuseꢀofꢀH ꢀasꢀanꢀ
electronꢀacceptorꢀenhancedꢀglycerolꢀconversionꢀmoreꢀthanꢀO . Theꢀtypeꢀofꢀgeneratedꢀvalue‐addedꢀ
compoundsꢀdependedꢀonꢀtheꢀconcentrationꢀofꢀtheꢀgeneratedꢀROS.ꢀ
ꢀ2016,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.

1
tronꢀacceptors,ꢀbothꢀHO ꢀradicalꢀandꢀ O
2
2
O
2 2
Keywords:ꢀ
2
Glycerolꢀoxidationꢀ
Titaniumꢀdioxideꢀ
Photocatalystꢀ
©
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
Electronꢀacceptorꢀ
1.ꢀ ꢀ Introductionꢀ
stability,ꢀ andꢀ suitableꢀ bandꢀ gapꢀ energyꢀ [17].ꢀ Recently,ꢀ itꢀ wasꢀ
reportedꢀ thatꢀ theꢀ useꢀ ofꢀ TiO ꢀ inꢀ eitherꢀ anꢀ anataseꢀ orꢀ ru‐
2
Glycerolꢀisꢀaꢀchemicalꢀthatꢀcanꢀbeꢀappliedꢀinꢀvariousꢀindus‐
tile/anatase‐rutileꢀphaseꢀcanꢀenhanceꢀtheꢀpartialꢀphotocatalyticꢀ
oxidationꢀ ofꢀ glycerolꢀ toꢀ dihydroxyacetoneꢀ (DHA)ꢀ andꢀ glycer‐
triesꢀsuchꢀasꢀpharmaceutical,ꢀcosmetic,ꢀandꢀfoodꢀindustriesꢀ[1].ꢀ
Itꢀ isꢀ alsoꢀ aꢀ buildingꢀ blockꢀ chemicalꢀ thatꢀ canꢀ beꢀ convertedꢀ toꢀ
high‐valuedꢀ chemicalꢀ substancesꢀ suchꢀ asꢀ lacticꢀ acidꢀ [2–4],ꢀ
acrylicꢀacidꢀ[5–7],ꢀdihydroxyacetoneꢀ[8–11],ꢀacroleinꢀ[12–14],ꢀ
andꢀ propanedialꢀ [15]ꢀ usingꢀ processesꢀ suchꢀ asꢀ hydrothermalꢀ
aldehydeꢀ (GCD)ꢀ toꢀ giveꢀ selectivitiesꢀ ofꢀ 4.5%–8%ꢀ andꢀ 6.5%–
ꢀ
13%,ꢀrespectivelyꢀ[18].ꢀItꢀwasꢀalsoꢀreportedꢀthatꢀaꢀcylindricalꢀ
photoreactorꢀwasꢀmoreꢀefficientꢀthanꢀanꢀannularꢀphotoreactor.ꢀ
TheꢀtransformationꢀofꢀglycerolꢀinꢀtheꢀpresenceꢀofꢀTiO ꢀDegussaꢀ
2
[
3,4],ꢀoxidationꢀ[5–7,ꢀ9–11],ꢀdehydrationꢀ[12–14],ꢀandꢀelectro‐
P25ꢀ wasꢀ aꢀ functionꢀ ofꢀ theꢀ substrateꢀ concentration,ꢀ andꢀ theꢀ
generatedꢀproductsꢀwereꢀderivedꢀfromꢀaꢀdirectꢀelectronꢀtrans‐
chemicalꢀ treatmentꢀ [8,15,16].ꢀ Photocatalyticꢀ oxidationꢀ isꢀ aꢀ
processꢀthatꢀcanꢀconvertꢀglycerolꢀtoꢀvariousꢀvalue‐addedꢀcom‐
pounds.ꢀAlthoughꢀvariousꢀsemiconductorꢀmetalꢀoxidesꢀcanꢀbeꢀ
usedꢀ inꢀ aꢀ photocatalyticꢀ reaction,ꢀ includingꢀ TiO
SiO ,ꢀ ZrO ,ꢀ CeO ,ꢀ SnO ,ꢀ Fe ,ꢀ SrTiO ꢀ andꢀ BaTiO
mostꢀ widelyꢀ usedꢀ becauseꢀ ofꢀ itsꢀ highꢀ photocatalyticꢀ activity,ꢀ
ferꢀ[19].ꢀTiO ꢀinꢀtheꢀrutileꢀphaseꢀwithꢀaꢀhighꢀpercentageꢀofꢀ[110]ꢀ
2
facetsꢀ enhancedꢀ glycerolꢀ conversionꢀ andꢀ achievedꢀ overꢀ 90%ꢀ
selectivityꢀ toꢀ hydroxyacetadehydeꢀ (HAA),ꢀ whileꢀ anataseꢀ withꢀ
[001]ꢀ orꢀ [101]ꢀ facetsꢀ gaveꢀ onlyꢀ 16%ꢀ andꢀ 49%ꢀ selectivityꢀ forꢀ
HAA,ꢀrespectivelyꢀ[20].ꢀ
2 2 3
,ꢀ ZnO,ꢀ Al O ,ꢀ
2
2
2
2
O
2 3
3
3
,ꢀ TiO ꢀ isꢀ theꢀ
2
*ꢀCorrespondingꢀauthor. Tel:ꢀ+66ꢀ(2)ꢀ2187523‐5;ꢀFax:ꢀ+66ꢀ(2)ꢀ2555831;ꢀE‐mail:ꢀmali.h@chula.ac.thꢀ
DOI:ꢀ10.1016/S1872‐2067(16)62519‐6ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ37,ꢀNo.ꢀ11,ꢀNovemberꢀ2016 ꢀ

1976ꢀ
TrinꢀJedsukontornꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1975–1981ꢀ
Nevertheless,ꢀ theꢀ useꢀ ofꢀ bareꢀ TiO
2
ꢀ asꢀ aꢀ photocatalystꢀ stillꢀ
toryꢀ scaleꢀ atꢀ ambientꢀ conditions.ꢀ Onꢀ addition,ꢀ theꢀ reactionꢀ
pathwayꢀ forꢀ glycerolꢀ conversionꢀ viaꢀ TiO ‐inducedꢀ photocata‐
ꢀandꢀO ꢀasꢀanꢀ electronꢀ
gaveꢀ aꢀ slowꢀ rateꢀ ofꢀ glycerolꢀ conversion,ꢀ probablyꢀ dueꢀ toꢀ theꢀ
2

+
recombinationꢀofꢀh ‐e ꢀthatꢀoccurredꢀafterꢀtheꢀchargeꢀsepara‐
lyticꢀ oxidationꢀ inꢀ theꢀ presenceꢀ ofꢀ H
acceptorꢀwasꢀalsoꢀproposed.ꢀ
O
2 2
2
tionꢀwhenꢀTiO ꢀabsorbedꢀlightꢀwithꢀphotonꢀenergyꢀequalꢀtoꢀorꢀ
2
higherꢀthanꢀitsꢀbandꢀgapꢀenergy.ꢀThisꢀcausedꢀaꢀdecreaseꢀinꢀtheꢀ
+
photoinducedꢀh ꢀ[21].ꢀTwoꢀstrategiesꢀthatꢀcanꢀreduceꢀthisꢀre‐
2.ꢀ ꢀ Experimentalꢀ
combinationꢀproblemꢀareꢀtheꢀuseꢀofꢀaꢀmetal‐dopedꢀTiO
catalystꢀ andꢀtheꢀ useꢀofꢀ anꢀelectronꢀaccepter.ꢀ Byꢀusingꢀ aꢀmet‐
al‐dopedꢀTiO ,ꢀitꢀwasꢀreportedꢀthatꢀperoxideꢀisꢀtheꢀmainꢀoxida‐
tionꢀproductꢀoverꢀirradiatedꢀaqueousꢀPt/TiO ꢀunderꢀconditionsꢀ
ofꢀglycerolꢀ photoreformingꢀ fromꢀtwoꢀroutesꢀinvolvingꢀ(1)ꢀtheꢀ
oxidationꢀofꢀsurfaceꢀhydroxylꢀgroupsꢀbyꢀphotogeneratedꢀholesꢀ
andꢀ theꢀ subsequentꢀ dimerizationꢀ ofꢀ theꢀ so‐formedꢀ hydroxylꢀ
radicalsꢀandꢀ(2)ꢀtheꢀconsecutiveꢀreductionꢀofꢀsurface‐trappedꢀ
oxygenꢀbyꢀconductionꢀbandꢀelectronsꢀ[22].ꢀAꢀhighꢀproductionꢀ
rateꢀofꢀtheꢀhydroxylꢀradicalꢀcanꢀenhanceꢀaꢀhighꢀconversionꢀofꢀ
2
ꢀphoto‐
2.1.ꢀ ꢀ Chemicalsꢀandꢀcatalystꢀ
2
2
Allꢀchemicalsꢀusedꢀwereꢀanalyticalꢀgrade,ꢀincludingꢀglycerolꢀ
(GLY,ꢀ99.5%,ꢀQReC),ꢀH ꢀ(30ꢀwt%,ꢀQReC),ꢀO ꢀ(99.5%ꢀPraxair),ꢀ
O
2 2
2
DHAꢀ (98%,ꢀ Merck),ꢀ glycericꢀ acidꢀ (GCA,ꢀ 20ꢀ wt%,ꢀ TCI),ꢀ GCDꢀ
(98%,ꢀ Sigmaꢀ Aldrich),ꢀ glycoricꢀ acidꢀ (GCOA,ꢀ 70ꢀ wt%,ꢀ Ajaxꢀ
Finechem),ꢀ formicꢀ acidꢀ (FMA,ꢀ 98%,ꢀ Merck),ꢀ hydroxypyruvicꢀ
acidꢀ (HPA,ꢀ ≥ꢀ 95%,ꢀ Sigmaꢀ Aldrich),ꢀ andꢀ formaldehydeꢀ (FMD,ꢀ
37%,ꢀMerck).ꢀTheꢀphotocatalystꢀusedꢀwasꢀcommercialꢀanataseꢀ
glycerolꢀ andꢀ productꢀ generation.ꢀ Aꢀ nanotube‐structuredꢀ TiO
2
ꢀ
TiO ꢀ powderꢀ (Sigmaꢀ Aldrich).ꢀ Theꢀ probeꢀ compoundsꢀ usedꢀ toꢀ
2
(
TiNT)ꢀcanꢀenhanceꢀaꢀconversionꢀofꢀglycerolꢀtoꢀH
2
ꢀtoꢀtwiceꢀthatꢀ
monitorꢀ theꢀ generationꢀ ofꢀ theꢀ oxidizingꢀ speciesꢀ wereꢀ pa‐
ra‐chlorobenzoicꢀacidꢀ(pCBA,ꢀSigmaꢀAldrich)ꢀandꢀfurfurylꢀalco‐
holꢀ(FFA,ꢀSigmaꢀAldrich).ꢀ
ofꢀnanoparticleꢀTiO
2
ꢀ(P25).ꢀTheꢀdopingꢀofꢀTiNTꢀwithꢀPtꢀandꢀNꢀ
(
Pt‐N‐TiNT)ꢀcanꢀimproveꢀtheꢀactivityꢀforꢀglycerolꢀconversionꢀupꢀ
toꢀ13ꢀtimesꢀcomparedꢀwithꢀP25ꢀ[23].ꢀTheꢀrateꢀofꢀtheꢀphotore‐
formingꢀofꢀglycerolꢀtoꢀH ꢀandꢀCO ꢀwasꢀincreasedꢀbyꢀaꢀfactorꢀofꢀ
5ꢀ andꢀ 60,ꢀ respectively,ꢀ overꢀ Pt/TiO ꢀ comparedꢀ toꢀ theꢀ TiO ꢀ
2
2
2.2.ꢀ ꢀ Characterizationꢀ
2
2
2
photocatalyst,ꢀ whichꢀ wasꢀ dueꢀ toꢀ theꢀ increasedꢀ separationꢀ ofꢀ
h ‐e ꢀpairsꢀandꢀtheꢀpromotionꢀofꢀtheꢀrateꢀlimitingꢀcathodicꢀhalfꢀ
TheꢀBETꢀsurfaceꢀareaꢀofꢀtheꢀutilizedꢀcommercialꢀTiO
2
ꢀwasꢀ

+
measuredꢀ byꢀ N ꢀ adsorptionꢀ byꢀ theꢀ Brunauer‐Emmett‐Tellerꢀ
2
reactionsꢀinꢀtheꢀpresenceꢀofꢀmetallicꢀPtꢀ[24].ꢀ
(BET)ꢀtechniqueꢀwithꢀaꢀsurfaceꢀareaꢀanalyzerꢀ(Quantachrome,ꢀ
Autosorb‐1).ꢀ Itsꢀ bandꢀ gapꢀ energyꢀ wasꢀ determinedꢀ byꢀ aꢀ
UV‐Visibleꢀ spectrophotometerꢀ (Shimadzꢀ UV‐3600)ꢀ inꢀ theꢀ
wavelengthꢀ rangeꢀ ofꢀ 300–800ꢀ nmꢀ atꢀ roomꢀ temperature.ꢀ Theꢀ
bondingꢀ andꢀ valenceꢀ stateꢀ ofꢀ theꢀ metalsꢀ inꢀ theꢀ photocatalystꢀ
wereꢀdeterminedꢀusingꢀX‐rayꢀphotoelectronꢀspectroscopyꢀ(XPS,ꢀ
Toꢀ enhanceꢀ glycerolꢀ conversion,ꢀ theꢀ secondꢀ strategyꢀ wasꢀ
carriedꢀout.ꢀItꢀ wasꢀreportedꢀthatꢀdifferentꢀtypesꢀofꢀROSꢀ wereꢀ
producedꢀinꢀtheꢀpresenceꢀofꢀdifferentꢀelectronꢀacceptorsꢀasꢀwellꢀ

ꢀ
2 2 2
asꢀtheꢀTiO ꢀphase.ꢀInꢀtheꢀpresenceꢀofꢀH O ,ꢀtheꢀrateꢀofꢀOH for‐
mationꢀ increasedꢀ forꢀ rutileꢀ andꢀ anataseꢀ mixedꢀ withꢀ rutileꢀ ofꢀ
1
0%–20%,ꢀ whileꢀ pureꢀ anataseꢀ exhibitedꢀ anꢀ oppositeꢀ trendꢀ
PHIꢀ5000ꢀVersaProbeꢀIIꢀwithꢀmonochromatedꢀAlꢀK ꢀradiation).ꢀ ꢀ


[25].ꢀ Aꢀ higherꢀ productionꢀ rateꢀ ofꢀ O
2
ꢀ wasꢀ observedꢀ withꢀ theꢀ
TiO
2
ꢀinꢀtheꢀanataseꢀphaseꢀthanꢀthatꢀinꢀtheꢀrutileꢀphase.ꢀHowev‐
2.3.ꢀ ꢀ Glycerolꢀoxidationꢀ

er,ꢀinꢀtheꢀpresenceꢀofꢀO
inꢀtheꢀpresenceꢀofꢀTiO
anataseꢀphase.ꢀTheꢀuseꢀofꢀO
itateꢀtheꢀphotoreformingꢀofꢀglycerolꢀtowardꢀCO
thanꢀ anꢀ un‐metallizedꢀ TiO ,ꢀ whileꢀ theꢀ activityꢀ wasꢀ extremelyꢀ
highꢀ withꢀ theꢀ Pt/TiO
productionꢀofꢀOH ꢀandꢀsingletꢀoxygenꢀ( O
ROSꢀthatꢀcontributeꢀtoꢀphotodegradation,ꢀwasꢀmoreꢀthanꢀoneꢀ
2
,ꢀaꢀlargerꢀquantityꢀofꢀO
2
ꢀwasꢀgeneratedꢀ
2
ꢀinꢀtheꢀrutileꢀphaseꢀcomparedꢀwithꢀtheꢀ
ꢀasꢀanꢀelectronꢀacceptorꢀcouldꢀfacil‐
ꢀandꢀH ꢀmoreꢀ
Theꢀ conversionꢀ ofꢀ commercialꢀ glycerolꢀ gaveꢀ value‐addedꢀ
compoundsꢀ thatꢀ includedꢀ DHA,ꢀ GCA,ꢀ GCD,ꢀ GCOA,ꢀ FMA,ꢀ HPA,ꢀ
andꢀFMD,ꢀandꢀwasꢀcarriedꢀoutꢀinꢀaꢀhollowꢀcylindricalꢀglassꢀre‐
actorꢀhavingꢀaꢀdiameterꢀofꢀ10ꢀcm.ꢀTheꢀreactorꢀwasꢀplacedꢀinꢀtheꢀ
middleꢀofꢀaꢀUV‐protectedꢀboxꢀwithꢀtheꢀdimensionsꢀofꢀ0.68ꢀmꢀ×ꢀ
0.68ꢀ mꢀ ×ꢀ 0.78ꢀ m.ꢀ Aꢀ 120ꢀ Wꢀ UVꢀ highꢀ pressureꢀ mercuryꢀ lampꢀ
(RUVꢀ 533ꢀ BC,ꢀ Holland)ꢀ wasꢀ placedꢀ onꢀ theꢀ roofꢀ ofꢀ theꢀ
UV‐protectedꢀboxꢀasꢀpreviouslyꢀdescribedꢀ[30].ꢀ
2
2
2
2
2
ꢀ photocatalystꢀ [24]. However,ꢀ theꢀ finalꢀ

1
2
),ꢀwhichꢀareꢀtheꢀmainꢀ

orderꢀofꢀmagnitudeꢀhigherꢀthanꢀO
2
.ꢀ[26].ꢀTheꢀimportanceꢀofꢀtheꢀ

OH ꢀ radicalꢀ isꢀ understandableꢀ becauseꢀ ofꢀ itsꢀ highꢀ oxidizingꢀ
Inꢀeachꢀexperiment,ꢀ100ꢀmLꢀofꢀglycerolꢀ(0.3ꢀmol/L)ꢀwasꢀir‐
radiatedꢀwithꢀUVꢀlightꢀhavingꢀtheꢀintensityꢀofꢀ4.7ꢀmW/cm ꢀandꢀ

1
2
power.ꢀHowever,ꢀwithꢀotherꢀROSꢀspeciesꢀsuchꢀasꢀ O
2
ꢀandꢀO
2
,ꢀ
veryꢀlittleꢀworkꢀhasꢀbeenꢀcarriedꢀoutꢀtoꢀunderstandꢀtheirꢀfor‐
withꢀaꢀTiO2ꢀdosageꢀofꢀ3ꢀg/Lꢀforꢀ20ꢀh.ꢀTheꢀsolutionꢀwasꢀagitatedꢀ
continuouslyꢀ byꢀ aꢀ magneticꢀ stirrerꢀ atꢀ 300ꢀ r/minꢀ toꢀ achieveꢀ
completeꢀ mixing.ꢀ Twoꢀ typesꢀ ofꢀ electronꢀ acceptorꢀ includingꢀ

mationꢀinꢀaꢀphotocatayticꢀoxidationꢀsystem.ꢀInꢀaddition,ꢀO
2
ꢀcanꢀ
1
beꢀquicklyꢀconvertedꢀtoꢀ O2ꢀ[26],ꢀresultingꢀinꢀitsꢀlowerꢀconcen‐
1
2
trationꢀinꢀtheꢀ photocatalyticꢀ system.ꢀ O ꢀisꢀaꢀstrongꢀoxidationꢀ
H O
2
2
ꢀandꢀO ꢀwereꢀusedꢀforꢀtheirꢀeffectꢀonꢀglycerolꢀconversionꢀ
2
reagentꢀ forꢀ someꢀ organicꢀ compoundsꢀ [27,28]ꢀ dueꢀ toꢀ itsꢀ highꢀ
quantumꢀyieldꢀ[25].ꢀThisꢀsuggestsꢀthatꢀitꢀisꢀanꢀimportantꢀspe‐
andꢀ productꢀ distribution.ꢀ Theꢀ feedingꢀ procedureꢀ ofꢀ theꢀ twoꢀ
chemicalsꢀwasꢀslightlyꢀdifferentꢀdueꢀtoꢀtheirꢀdifferentꢀchemicalꢀ
ciesꢀforꢀtheꢀphotocatalyicꢀTiO
Inꢀtheꢀpresentꢀstudy,ꢀbothꢀH
tronꢀacceptorsꢀinꢀtheꢀphotocatalyticꢀoxidationꢀofꢀglycerolꢀwithꢀ
nanoparticleꢀTiO .ꢀTheꢀeffectsꢀofꢀtheseꢀelectronꢀacceptorsꢀonꢀtheꢀ
typeꢀofꢀgeneratedꢀROSꢀ(especiallyꢀOH andꢀ O
version,ꢀandꢀproductꢀdistributionꢀwereꢀexploredꢀonꢀtheꢀlabora‐
2
ꢀaqueousꢀsuspensionꢀ[25–29].ꢀ
phases.ꢀTheꢀtotalꢀrequiredꢀvolumeꢀofꢀH
mol/Lꢀandꢀ3.06ꢀmLꢀforꢀ0.3ꢀmol/L)ꢀwasꢀaddedꢀintoꢀtheꢀglycerolꢀ
solutionꢀpriorꢀtoꢀstartingꢀtheꢀreaction,ꢀwhileꢀO ꢀwasꢀfedꢀcontin‐
uouslyꢀatꢀaꢀconstantꢀflowꢀrateꢀofꢀ200ꢀmL/min.ꢀAsꢀtheꢀexperi‐
mentꢀprogressed,ꢀ2ꢀmLꢀsamplesꢀwereꢀcollectedꢀandꢀquenchedꢀ
inꢀanꢀice‐waterꢀtrapꢀatꢀ0ꢀ°Cꢀtoꢀterminateꢀtheꢀreactionꢀandꢀthenꢀ
2
O ꢀ(0.765ꢀmLꢀforꢀ0.075ꢀ
2
2 2
O
ꢀandꢀO ꢀwereꢀusedꢀasꢀelec‐
2
2
2

1
2
),ꢀglycerolꢀcon‐

ꢀ
TrinꢀJedsukontornꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1975–1981ꢀ
1977ꢀ
centrifugedꢀonꢀaꢀKUBOTAꢀKC‐25ꢀDigitalꢀLaboratoryꢀCentrifugeꢀ
toꢀseparateꢀtheꢀsolidꢀcatalystꢀfromꢀtheꢀaqueousꢀproduct.ꢀ
Theꢀconcentrationsꢀofꢀglycerolꢀandꢀgeneratedꢀproductsꢀwereꢀ
analyzedꢀbyꢀaꢀhighꢀperformanceꢀliquidꢀchromatographyꢀ(HPLC)ꢀ
withꢀ aꢀ RID‐10Aꢀrefractiveꢀindexꢀdetectorꢀ (Agilentꢀ 1100).ꢀTheꢀ
stationaryꢀphaseꢀwasꢀAminexꢀHPX‐87Hꢀionꢀexclusionꢀ(300ꢀmmꢀ
3
2
1
0
5
4
3
2
1
0
ꢀ7.8ꢀmm),ꢀandꢀtheꢀmobileꢀphaseꢀwasꢀaꢀwater‐acetonitrileꢀsolu‐
tionꢀ(65:35ꢀV/V)ꢀwithꢀH SO ꢀ(0.5ꢀmmol/L)ꢀatꢀaꢀconstantꢀflowꢀ
2
4
rateꢀofꢀ0.5ꢀmL/min.ꢀStandardꢀsolutionsꢀofꢀglycerolꢀandꢀexpectedꢀ
majorꢀproductꢀcompoundsꢀwereꢀusedꢀtoꢀidentifyꢀtheꢀretentionꢀ
timeꢀandꢀdetermineꢀtheꢀrelationshipꢀbetweenꢀtheꢀpeakꢀareaꢀandꢀ
concentration.ꢀ
3.1
3.2
3.3
3.4
3.5
Photon energy (eV)
300
400
500
Wavelength (nm)
Fig.ꢀ1.ꢀUV-visibleꢀspectraꢀandꢀ(inset)ꢀtheꢀdependenceꢀofꢀ(hv)1/2ꢀonꢀtheꢀ
photonꢀenergyꢀofꢀTiO powder.ꢀ
600
700
800
Theꢀ conversionꢀ ofꢀ glycerolꢀ (X)ꢀ andꢀ theꢀ yieldꢀ ofꢀ theꢀ moni‐
toredꢀproductsꢀ(Y)ꢀofꢀtheꢀphotocatalyticꢀoxidationꢀwereꢀcalcu‐
latedꢀbasedꢀonꢀcarbonꢀusingꢀEqs.ꢀ(1)ꢀandꢀ(2),ꢀrespectively.ꢀTheꢀ
dataꢀreportedꢀwereꢀtheꢀaverageꢀvaluesꢀobtainedꢀfromꢀatꢀleastꢀ
threeꢀexperimentsꢀandꢀtheꢀerrorꢀinꢀthisꢀworkꢀwasꢀ3%.ꢀ
Molesꢀofꢀglycerolꢀconverted
2
peakꢀshapeꢀofꢀTiꢀ2pꢀassignedꢀtoꢀtheꢀcomponentꢀofꢀTiꢀ2p1/2ꢀandꢀ
Tiꢀ2p3/2ꢀatꢀtheꢀbindingꢀenergiesꢀofꢀ465.2ꢀandꢀ459.4ꢀeV,ꢀrespec‐
ꢁ
ꢂ
ꢃ 100% ꢀ ꢀ ꢀ ꢀ ꢀ (1)
TotalꢀMolesꢀofꢀglycerol inꢀreactant
ꢀ
tively,ꢀwhichꢀconfirmedꢀtheꢀstateꢀofꢀTiꢀasꢀTi4+ꢀinꢀtheꢀTiO
struc‐
2
Molesꢀofꢀglycerolꢀconvertedꢀtoꢀproductꢀꢅ
TotalꢀMolesꢀofꢀglycerol inꢀreactantꢀ
ture.ꢀInꢀtheꢀOꢀ1sꢀXPSꢀspectraꢀ(insertꢀofꢀFig.ꢀ2),ꢀtheꢀmainꢀOꢀ1sꢀ
peakꢀ appearedꢀ atꢀ theꢀ bindingꢀ energiesꢀ betweenꢀ 530.2–530.6ꢀ
eV,ꢀ531.8–532.0ꢀeVꢀ andꢀ533.0ꢀeV,ꢀ assignedꢀtoꢀtheꢀ Oꢀ1sꢀpeaksꢀ
characteristicꢀofꢀO
3.2.ꢀ ꢀ Glycerolꢀconversionꢀandꢀproductꢀdistributionꢀ
Toꢀ exploreꢀ theꢀ effectꢀ ofꢀ electronꢀ acceptorꢀ onꢀ theꢀ TiO2‐in‐
ꢄ ꢂ
ꢃ 100% ꢀ ꢀ ꢀ (2)
ꢀ


ꢀ
2.4.ꢀ ꢀ MeasurementꢀofꢀROSꢀ
2
,ꢀOH andꢀadsorbedꢀH O,ꢀrespectively.ꢀ
2

ꢀ
1
2
Bothꢀ ROS,ꢀ includingꢀ theꢀ OH radicalꢀ andꢀ O
,ꢀ wereꢀ deter‐

ꢀ
minedꢀbyꢀusingꢀspecificꢀscavengers.ꢀTheꢀproductionꢀofꢀtheꢀOH
radicalꢀwasꢀmonitoredꢀbyꢀtheꢀlossꢀofꢀpCBAꢀ[31,32].ꢀTheꢀproduc‐
ꢀ
1
tionꢀofꢀ O
2
ꢀwasꢀmonitoredꢀbyꢀtheꢀlossꢀofꢀFFAꢀ[32].ꢀTheꢀconcen‐
ducedꢀ photocatalyticꢀ oxidationꢀ ofꢀ glycerol,ꢀ twoꢀ typesꢀ ofꢀ elec‐
tronꢀacceptors,ꢀH O ꢀandꢀO ,ꢀwereꢀutilized.ꢀAꢀblankꢀexperimentꢀ
wasꢀfirstꢀcarriedꢀoutꢀwithꢀtheꢀpresenceꢀofꢀeitherꢀH O ꢀorꢀO ,ꢀbutꢀ
trationꢀ variationꢀ ofꢀ pCBAꢀ andꢀ FFAꢀ wasꢀ analyzedꢀ byꢀ HPLCꢀ
equippedꢀwithꢀaꢀPinnacleꢀIIꢀC18ꢀcolumnꢀ(240ꢀmmꢀ×ꢀ4.6ꢀmm).ꢀ
Theꢀ mobileꢀ phaseꢀ wasꢀ methanol‐water‐acetonitrileꢀ (55:35:10ꢀ
2
2
2
2
2
2
theꢀ absenceꢀ ofꢀ bothꢀ UVꢀ lightꢀ andꢀ TiO .ꢀ Itꢀ wasꢀ foundꢀ thatꢀ theꢀ
2
2 4
V/V)ꢀ withꢀ H SO ꢀ (10ꢀ mmol/L)ꢀ forꢀ pCBAꢀ detection.ꢀ Aꢀ 50/50ꢀ
presenceꢀofꢀonlyꢀH O ꢀorꢀO ꢀcannotꢀfacilitateꢀtheꢀconversionꢀofꢀ
2
2
2
(
V/V)ꢀsolventꢀmixtureꢀofꢀwater‐ethanolꢀwasꢀusedꢀasꢀtheꢀmobileꢀ
glycerol.ꢀHowever,ꢀtheꢀpresenceꢀofꢀirradiatedꢀUVꢀlightꢀandꢀTiO2ꢀ
inꢀtheꢀabsenceꢀofꢀH O ꢀorꢀO ꢀpromotedꢀtheꢀconversionꢀofꢀglyc‐
phaseꢀforꢀFFAꢀdetermination.ꢀTheꢀ10ꢀμLꢀsampleꢀinjectedꢀpassedꢀ
throughꢀtheꢀcolumnꢀwithꢀaꢀconstantꢀflowꢀrateꢀofꢀ0.5ꢀmL/min.ꢀ
2
2
2
erolꢀtoꢀfourꢀvalue‐addedꢀcompounds,ꢀDHA,ꢀGCA,ꢀGCDꢀandꢀGCOAꢀ
Fig.ꢀ3(a)).ꢀTheꢀadditionꢀofꢀH ꢀintoꢀtheꢀirradiatedꢀUVꢀlightꢀandꢀ
TiO ꢀ systemꢀ furtherꢀenhancedꢀ theꢀ conversionꢀ ofꢀ glycerolꢀandꢀ
(
O
2 2
3
.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
2
gaveꢀoneꢀadditionalꢀproduct,ꢀFMAꢀ(Fig.ꢀ3(b)).ꢀUsingꢀO
2
ꢀasꢀelec‐
3.1.ꢀ ꢀ Catalystꢀcharacterizationꢀ
tronꢀ acceptorꢀ insteadꢀ ofꢀ H O ꢀ decreasedꢀ theꢀ glycerolꢀ conver‐
2
2
sionꢀ toꢀ almostꢀ halfꢀ (Fig.ꢀ 3(c)).ꢀ Theꢀ glycerolꢀ conversionꢀ wasꢀ
aboutꢀ50%ꢀatꢀ20ꢀh.ꢀTheꢀsameꢀthreeꢀvalue‐addedꢀcompounds,ꢀ
DHA,ꢀ GCDꢀ andꢀ GCOA,ꢀ wereꢀ stillꢀ observed,ꢀ whileꢀ twoꢀ moreꢀ
Theꢀ photocatalystꢀ utilizedꢀ wasꢀ commercialꢀ TiO
BETꢀsurfaceꢀareaꢀofꢀ22.84ꢀm /gꢀandꢀparticleꢀsizeꢀofꢀlessꢀthanꢀ25ꢀ
2
ꢀ havingꢀ aꢀ
2
nm.ꢀ Figureꢀ 1ꢀ exhibitsꢀ theꢀ opticalꢀ absorptionꢀ spectraꢀ ofꢀ TiO
2
ꢀ
recordedꢀ usingꢀ aꢀ UV‐visibleꢀ spectrophotometerꢀ inꢀ theꢀ wave‐
lengthꢀrangeꢀofꢀ300–800ꢀnmꢀatꢀroomꢀtemperature.ꢀAꢀdecreaseꢀ
ofꢀabsorbanceꢀtoꢀaꢀzeroꢀvalueꢀwasꢀobservedꢀinꢀtheꢀvisibleꢀlightꢀ
regionꢀatꢀwavelengthsꢀaboveꢀ450ꢀnm,ꢀshowingꢀitsꢀUVꢀlightꢀab‐
sorptionꢀability.ꢀByꢀusingꢀtheꢀlinearꢀportionꢀofꢀtheꢀfundamentalꢀ
absorptionꢀedgeꢀofꢀitsꢀspectra,ꢀtheꢀplotꢀofꢀ(αhv)1/nꢀagainstꢀ(hv)ꢀ ꢀ
O 1s
(insetꢀofꢀFig.ꢀ 1),ꢀwhereꢀαꢀ isꢀtheꢀopticalꢀ absorptionꢀcoefficientꢀ
526 528 530 532 534 536 538
determinedꢀfromꢀtheꢀobtainedꢀabsorbanceꢀandꢀhvꢀisꢀtheꢀenergyꢀ
Binding energy (eV)
ofꢀ theꢀ incidentꢀ photons,ꢀ providedꢀ theꢀ valueꢀ ofꢀ theꢀ bandꢀ bapꢀ
energyꢀ (E
agreedꢀwithꢀtheꢀtheoreticalꢀbandꢀgapꢀenergyꢀofꢀanataseꢀTiO
WithꢀregardꢀtoꢀtheꢀbondingꢀandꢀvalenceꢀstateꢀofꢀTi,ꢀasꢀshownꢀ
inꢀFig.ꢀ2,ꢀtheꢀXPSꢀ spectraꢀofꢀtheꢀ TiO ꢀ showedꢀtwoꢀ symmetricꢀ
g
).ꢀ Theꢀ bandꢀ gapꢀ energyꢀ ofꢀ TiO
2
ꢀ wasꢀ 3.2ꢀ eV,ꢀ whichꢀ
2
.ꢀ
456
461
466
471
476
Bindind energy (eV)
2
Fig.ꢀ2.ꢀXPSꢀspectraꢀofꢀtheꢀcommercialꢀTiO
2
ꢀpowder.ꢀ

1978ꢀ
TrinꢀJedsukontornꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1975–1981ꢀ
60
50
40
30
20
10
0
100
1
.0
DHA
GCA
GCD
GCOA
Conversion
(a)
(a)
UV light/TiO2
UV light/TiO
iOt/
UV light/TiO2/O2
2
80
0.8
U
U
V
V
lig
l
h
i
t
g
/T
h
2
T
/
i
H
O
2O
/
2
H O
2
2
2
2
UV light/TiO
/O
0
0
0
0
.6
.4
.2
.0
2
60
40
20
0
0
2
4
6
8
0
0
0
4
8
8
8
12
12
12
16
16
16
20
20
20
Time (h)
Time (h)
1
0
.0
.8
U
U
V
V
li
li
li
l
g
i gh t
i gh t/ Tt /
i gh t/ Tt /
h
/ Tt /
i
T
O
iO
2
6
5
4
3
2
1
0
0
0
0
0
0
0
100
(b)
2
DHA
GCA
GCD
GCOA
FMA
U
U
V
V
V
l
g
l
g
h
i
T
O
i
i
2
O
/H
/
2
H
O2
O
2
2
2
U
U
V
h
i
T
O
2
O
/O
/
2
O
2
2
(b)
80
60
40
20
0
0.6
0.4
Conversion
0
0
.2
.0
0
2
4
6
8
Time (h)
Fig.ꢀ4.ꢀVariationꢀofꢀ(a)ꢀpCBAꢀandꢀ(b)ꢀFFAꢀasꢀaꢀfunctionꢀofꢀtimeꢀinꢀtheꢀ
irradiatedꢀUVꢀlightꢀandꢀTiO2ꢀsystemꢀinꢀtheꢀpresenceꢀofꢀH ꢀandꢀO ꢀasꢀ
electronꢀacceptors.ꢀ
4
2
O
2
2
Time (h)
60
50
40
30
20
10
0
100
80
DHA
GCD
GCOA
HPA
FMD
(
c)
ofꢀpCBAꢀdecreasedꢀslightlyꢀasꢀtheꢀreactionꢀtimeꢀincreased,ꢀwhileꢀ
thatꢀofꢀFFAꢀremainedꢀconstantꢀ(Fig.ꢀ4(b)).ꢀThisꢀsuggestedꢀtheꢀ
formationꢀ ofꢀ HO ꢀ radicalsꢀinꢀtheꢀirradiatedꢀUVꢀlightꢀ andꢀTiO

60
40
20
0
2
ꢀ
Conversion
1
system,ꢀ butꢀ noꢀ O
2
.ꢀ Whenꢀ eitherꢀ H
2
O
2
ꢀ orꢀ O ꢀ wasꢀ usedꢀ asꢀ anꢀ
2
electronꢀ acceptor,ꢀ theꢀ concentrationꢀ ofꢀ pCBAꢀ andꢀ FFAꢀ de‐
creasedꢀ significantly,ꢀ suggestingꢀ theꢀ formationꢀ ofꢀ bothꢀ HO ꢀ

1
radicalꢀandꢀ O
2
ꢀinꢀtheꢀsystem.ꢀ ꢀ
Basedꢀonꢀtheꢀresultsꢀandꢀliteratureꢀreports,ꢀtheꢀgenerationꢀ

1
ofꢀHO ꢀradicalsꢀandꢀ O
Whenꢀ TiO
2
ꢀinꢀthisꢀstudyꢀcanꢀbeꢀproposedꢀasꢀfollows.ꢀ
ꢀ absorbedꢀ lightꢀ havingꢀ energyꢀ equalꢀ toꢀ orꢀ greaterꢀ
thanꢀitsꢀbandꢀgapꢀenergyꢀ(Ebg),ꢀanꢀelectronꢀ(e )ꢀisꢀexcitedꢀfromꢀ
theꢀvalenceꢀbandꢀintoꢀtheꢀconductionꢀband,ꢀleavingꢀaꢀpositiveꢀ
4
Time (h)
2

Fig.ꢀ3.ꢀPhotocatalyticꢀconversionꢀofꢀglycerolꢀ(0.3ꢀmol/L)ꢀ andꢀyieldꢀofꢀ
productsꢀ versusꢀ timeꢀ overꢀ (a)ꢀ UVꢀ light/TiO ,ꢀ (b)ꢀ UVꢀ light/TiO /H
0.3ꢀmol/L)ꢀandꢀ(c)ꢀUVꢀlight/TiO /O .ꢀ
2
2
O
2 2
(
2
2
+
holeꢀ(h )ꢀinꢀtheꢀvalenceꢀbandꢀaccordingꢀtoꢀEq.ꢀ(3)ꢀ[22].ꢀ
ꢆꢇꢈꢉbg

+
compoundsꢀwereꢀgeneratedꢀinꢀthisꢀsystem:ꢀHPAꢀandꢀFMD.ꢀ
.3.ꢀ ꢀ Oxygenꢀspeciesꢀ ꢀ
Asꢀpreviouslyꢀreported,ꢀtheꢀoxidationꢀofꢀglycerolꢀproceededꢀ
TiO
2
ꢀ
ꢊꢋꢋꢋꢌꢀ h ꢀ +ꢀ e ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ
ꢀ
(3)ꢀ
Inꢀtheꢀabsenceꢀofꢀanꢀelectronꢀacceptor,ꢀtheꢀphotogeneratedꢀ
holeꢀ oxidizedꢀ surfaceꢀ bondedꢀ waterꢀ moleculesꢀ toꢀ produceꢀ
highlyꢀreactiveꢀOH ꢀradicals,ꢀwhileꢀtheꢀgeneratedꢀe ꢀcanꢀfurtherꢀ
3


+
reactꢀwithꢀprotonꢀ(H )ꢀtoꢀformꢀgaseousꢀH
2
ꢀaccordingꢀtoꢀEqs.ꢀ(4)ꢀ
viaꢀtheꢀphotogeneratedꢀoxidizingꢀspecies,ꢀincludingꢀphotogen‐
andꢀ(5)ꢀ[22,36,37].ꢀ

+

+
+
ꢀ ꢀ
ꢀ
h ꢀ +ꢀ H Oꢀ ꢀ OH ꢀ +ꢀ H ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (4)ꢀ
eratedꢀ holesꢀ (h )ꢀ [33],ꢀ HO ꢀ radicalꢀ [34],ꢀ andꢀ oxideꢀ radicalsꢀ
2


+
(1
ꢀ ꢀ
e ꢀ +ꢀ H ꢀ ꢀ 1/2H ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (5)ꢀ
O /O
2 2
)ꢀ[35]ꢀformedꢀinꢀtheꢀphoto‐cleavageꢀofꢀwaterꢀandꢀH
2 2
O ꢀ
2

ꢀ
[22].ꢀToꢀmonitorꢀtheꢀtypeꢀofꢀROSꢀgeneratedꢀinꢀtheꢀsystemꢀinꢀtheꢀ
AsꢀexhibitedꢀinꢀFig.ꢀ4(a),ꢀaꢀsmallꢀquantityꢀofꢀOH radicalsꢀwasꢀ
presenceꢀofꢀbothꢀH ꢀandꢀO ,ꢀparallelꢀreactionsꢀwereꢀcarriedꢀ
2
O
2
2
producedꢀ inꢀ thisꢀ case,ꢀ probablyꢀ dueꢀ toꢀ theꢀ recombinationꢀ ofꢀ
h ‐e pairs,ꢀwhichꢀusuallyꢀoccurredꢀinꢀtheꢀabsenceꢀofꢀanꢀelectronꢀ
acceptor.ꢀThisꢀwasꢀconfirmedꢀbyꢀaꢀlowꢀglycerolꢀconversionꢀandꢀ

+
ꢀ
outꢀtoꢀmonitorꢀtheꢀproductionꢀofꢀtheꢀtwoꢀstrongꢀROS,ꢀincludingꢀ

ꢀ
1
theꢀHO radicalsꢀandꢀ O
2
.ꢀTheꢀproductionꢀofꢀtheꢀformerꢀspeciesꢀ
wasꢀtracedꢀbyꢀtheꢀconcentrationꢀlossꢀofꢀpCBAꢀ[31,32],ꢀwhileꢀtheꢀ
generationꢀofꢀtheꢀlatterꢀspeciesꢀwasꢀmonitoredꢀbyꢀtheꢀconcen‐
productꢀyieldꢀasꢀdemonstratedꢀinꢀFig.ꢀ3(a).ꢀ

Inꢀtheꢀpresenceꢀofꢀanꢀelectronꢀacceptor,ꢀe.g.ꢀH
2 2
O
,ꢀbothꢀOH ꢀ
1
trationꢀlossꢀofꢀFFAꢀ[32].ꢀMoreꢀdecreaseꢀofꢀtheꢀpCBAꢀ andꢀ FFAꢀ
radicalsꢀandꢀ O
2
ꢀwereꢀgenerated.ꢀVariousꢀelementaryꢀreactionsꢀ

ꢀ
canꢀthenꢀproceedꢀasꢀfollows.ꢀTheꢀH O ꢀcanꢀbreakꢀdownꢀtoꢀformꢀ
concentrationsꢀindicatedꢀaꢀhigherꢀgenerationꢀrateꢀofꢀHO radicalꢀ
2 2

ꢀ
1
OH radicalsꢀ(Eq.ꢀ(6))ꢀwhenꢀitꢀabsorbsꢀUVꢀlightꢀ[38,39].ꢀItꢀcanꢀ
andꢀ O
AsꢀdemonstratedꢀinꢀFig.ꢀ4(a),ꢀunderꢀirradiatedꢀUVꢀlightꢀandꢀ
TiO ꢀandꢀtheꢀabsenceꢀofꢀanꢀelectronꢀacceptor,ꢀtheꢀconcentrationꢀ
2
,ꢀrespectively.ꢀ
alsoꢀreactꢀviaꢀtheꢀphotogeneratedꢀelectronsꢀorꢀphotogeneratedꢀ
holesꢀaccordingꢀtoꢀEqs.ꢀ(7)ꢀandꢀ(8)ꢀtoꢀformꢀOH radicalsꢀ[40].ꢀ

ꢀ
2

ꢀ
TrinꢀJedsukontornꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1975–1981ꢀ
1979ꢀ

H
2
O
2
ꢀ ꢀ OH ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (6)ꢀ
1.0
1.0


–
H
2
O
2
ꢀ +ꢀ e ꢀ ꢀ HO ꢀ +ꢀ OH ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (7)ꢀ
UV light/TiO /H O (0.075 mol/L)
UV light/TiO2/0.075 M H2O2
2
2
2
+

H
2
O
2
ꢀ +ꢀ h ꢀ ꢀ 2OH ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (8)ꢀ
0.8
0.6
0.8
0.6
0.4
0.2
0.0
U
U
V
V l
l
i
i
g
g
h
h
t/
t
T
/ Ti Oi O2 /0
/
.
H
M
2
300 H
O (0.
2
3
O
0
2
0 mol/L
)
2
2

Furthermore,ꢀ itꢀ canꢀ oxidizeꢀ viaꢀ theꢀ formedꢀ HO ꢀ andꢀ theꢀ
photogeneratedꢀholesꢀasꢀwellꢀasꢀtheꢀOH ꢀradicalsꢀtoꢀformꢀO
radicals,ꢀ whichꢀ readilyꢀ reactꢀ withꢀ H


2
ꢀ

2
O ꢀ toꢀ formꢀ HO ꢀ radicalsꢀ
2
0
.4
0.2
.0
accordingꢀtoꢀEqs.ꢀ(9)–(11),ꢀrespectivelyꢀ[25,41].ꢀAlso,ꢀtheꢀgen‐


+
+
eratedꢀO
2ꢀ toꢀ formꢀ 1
Eqs.(12)–(14)).ꢀBothꢀgeneratedꢀROSꢀhaveꢀtheꢀabilityꢀtoꢀoxidizeꢀ
2
ꢀradicalsꢀcanꢀfurtherꢀreactꢀwithꢀh ꢀandꢀH ꢀasꢀwellꢀasꢀ

H
(
2
O
O ꢀ andꢀ HO ꢀ radicalsꢀ asꢀ describedꢀ aboveꢀ
2
0
0
1
2
3
4
5
6
7
8
glycerolꢀtoꢀformꢀvariousꢀproductsꢀasꢀshownꢀinꢀFig.ꢀ3(b).ꢀ ꢀ
Time (h)




+
H
2
O
2
ꢀ +ꢀ 2HO ꢀ +ꢀ h ꢀ ꢀ O
2
ꢀ +ꢀ 2H
2
Oꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (9)ꢀ
Oꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (10)ꢀ
Fig.ꢀ5.ꢀVariationꢀofꢀpCBAꢀandꢀFFAꢀasꢀaꢀfunctionꢀofꢀtimeꢀinꢀtheꢀpresenceꢀ


H
2
2
O ꢀ +ꢀ OH ꢀ +ꢀ HO ꢀ ꢀ O
2
ꢀ +ꢀ 2H
2
ofꢀH
2
O
2
ꢀatꢀdifferentꢀconcentrations.ꢀ



H
2
O
2
ꢀ +ꢀ O
2
ꢀ ꢀ OH ꢀ +ꢀ HO ꢀ +ꢀ O
2
ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (11)ꢀ

+
1
O
2
ꢀ +ꢀ h ꢀ ꢀ O
2
ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (12)ꢀ
60
100
80
ꢀ +ꢀ O

DHA
(a)
+
1
O
2
2
ꢀ +ꢀ 2H ꢀ ꢀ H
2
O
2
ꢀ +ꢀ O
2
ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (13)ꢀ
50
40
30
GCA



1
O
2
ꢀ +ꢀ H
Regardingꢀ theꢀ useꢀ ofꢀ O
possibleꢀ reactionsꢀ canꢀ beꢀ proposed.ꢀ Initially,ꢀ theꢀ suppliedꢀ O
2
O
2
ꢀ ꢀ O
2
ꢀ +ꢀ HO ꢀ +ꢀ OH ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (14)ꢀ
GCD
2
ꢀ asꢀ anꢀ electronꢀ acceptor,ꢀ variousꢀ
GCOA
HPA
60
2
ꢀ


canꢀ reactꢀ withꢀ theꢀ photogeneratedꢀ e ꢀ toꢀ formꢀ O
2

ꢀ (Eq.ꢀ (15))ꢀ
Conversion
40
20
0

20
10
0
andꢀ H
furtherꢀreactꢀwithꢀh ꢀandꢀH ꢀasꢀwellꢀasꢀH
radicalsꢀ(Eqs.ꢀ(12)–(14)).ꢀBesides,ꢀtheꢀgeneratedꢀH
sociateꢀafterꢀabsorbingꢀUVꢀlightꢀorꢀreactꢀwithꢀeitherꢀphotogen‐
2
O
2
ꢀ (Eq.ꢀ (16))ꢀ[26,ꢀ36].ꢀTheꢀgeneratedꢀ O
2
ꢀradicalsꢀcanꢀ
1
+
+
ꢀ
2 2
O ꢀtoꢀformꢀ O
2
ꢀandꢀHO
2 2
O ꢀcanꢀdis‐
0
4
8
12
16
20
+
–

Time (h)
eratedꢀh ꢀorꢀe ꢀtoꢀformꢀOH ꢀradicalsꢀaccordingꢀtoꢀEqs.ꢀ(9)–(11).ꢀ


60
50
40
100
80
O
2
ꢀ +ꢀ e ꢀ ꢀ O
2
ꢀ
ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (15)ꢀ
ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (16)ꢀ
DHA
GCA
GCD
GCOA
FMA

+
O
2
ꢀ +ꢀ 2e ꢀ +ꢀ 2H ꢀ ꢀ H
O
2 2
(b)
Theꢀ mechanismꢀ ofꢀ glycerolꢀ conversionꢀ toꢀ value‐addedꢀ
compoundsꢀunderꢀirradiatedꢀUVꢀlightꢀandꢀTiO ꢀinꢀtheꢀabsenceꢀ
andꢀpresenceꢀofꢀH ꢀhasꢀalreadyꢀbeenꢀproposedꢀinꢀpublishedꢀ
workꢀ[30,43].ꢀInꢀbrief,ꢀinꢀtheꢀabsenceꢀofꢀH ,ꢀtheꢀphotogener‐
2
Conversion
60
O
2 2
30
O
2
40
2
2
0
0
0
+

atedꢀh ꢀandꢀtheꢀOH ꢀradicalsꢀcanꢀattachꢀtoꢀtheꢀ1°‐ꢀorꢀ2°‐ꢀCꢀatomꢀ
ofꢀglycerolꢀtoꢀformꢀGCDꢀorꢀDHA,ꢀrespectivelyꢀ[44].ꢀThen,ꢀtheyꢀ
canꢀfurtherꢀoxidizeꢀtheꢀgeneratedꢀGCDꢀtoꢀformꢀGCAꢀasꢀwellꢀasꢀ
cleaveꢀtheꢀC–CꢀbondꢀofꢀGCAꢀtoꢀformꢀGCOAꢀ[45].ꢀOurꢀpreviousꢀ
workꢀdemonstratedꢀthatꢀDHAꢀcanꢀbeꢀoxidizedꢀtoꢀGCAꢀandꢀGCOAꢀ
20
1
0
0
4
8
12
16
20
Time (h)
[
36].ꢀ Highꢀ glycerolꢀ conversionꢀ andꢀyieldꢀofꢀvalue‐addedꢀ com‐
Fig.ꢀ6.ꢀPhotocatalyticꢀandꢀcatalyticꢀconversionꢀofꢀglycerolꢀ(0.3ꢀmol/L)
andꢀ yieldꢀ ofꢀ productsꢀ versusꢀ timeꢀ inꢀ theꢀ presenceꢀ ofꢀ (a)ꢀ UVꢀ light/
poundsꢀ wereꢀ observedꢀ inꢀ theꢀ presenceꢀ ofꢀ H
probablyꢀdueꢀtoꢀtheꢀlargeꢀamountsꢀofꢀbothꢀOH radicalꢀandꢀ O2ꢀ
generatedꢀasꢀwellꢀasꢀtheirꢀhighꢀoxidizingꢀpower.ꢀ ꢀ
2
O
2
,ꢀ whichꢀ wasꢀ
TiO
2
/H
2
O
2
ꢀ(0.075ꢀmol/L)ꢀandꢀ(b)ꢀUVꢀlight/TiO
2
/H
2
O ꢀ(0.3ꢀmol/L).ꢀ
2

ꢀ
1
poundsꢀ producedꢀ atꢀ lowꢀ H
typesꢀofꢀvalue‐addedꢀcompoundsꢀwasꢀalmostꢀtheꢀsameꢀasꢀthoseꢀ
generatedꢀ inꢀ theꢀ presenceꢀ ofꢀ aꢀ highꢀ H O ꢀ concentrationꢀ (Fig.ꢀ
2 2
O ꢀ concentrationsꢀ (Fig.ꢀ 6(a)),ꢀ theꢀ
2
Inꢀ theꢀ presenceꢀ ofꢀ O ,ꢀ differentꢀ value‐addedꢀ compoundsꢀ
wereꢀproduced,ꢀparticularlyꢀHPAꢀandꢀFMD.ꢀFromꢀtheꢀresults,ꢀitꢀ
seemsꢀ thatꢀ theꢀ typeꢀ ofꢀ generatedꢀ ROS,ꢀ includingꢀ OH ꢀ radicalꢀ

2 2
1
6(b))ꢀbutꢀinꢀlowꢀquantitiesꢀexceptꢀforꢀFMA.ꢀSurprisingly,ꢀHPAꢀ
wasꢀobservedꢀinꢀthisꢀsystem,ꢀwhichꢀindicatedꢀthatꢀtheꢀquantityꢀ
ofꢀtheꢀROSꢀpresentꢀaffectedꢀtheꢀrouteꢀofꢀglycerolꢀconversionꢀasꢀ
wellꢀasꢀtheꢀtypeꢀofꢀgeneratedꢀproducts.ꢀInꢀtheꢀpresenceꢀofꢀaꢀlowꢀ
andꢀ O
producedꢀfromꢀglycerolꢀconversionꢀbecauseꢀbothꢀspeciesꢀwereꢀ
producedꢀwhenꢀeitherꢀH ꢀorꢀO ꢀwasꢀusedꢀasꢀtheꢀelectronꢀac‐
ceptor.ꢀ Thisꢀ differenceꢀ wasꢀ probablyꢀ dueꢀ toꢀ theꢀ differenceꢀ inꢀ
theꢀROSꢀconcentrationꢀproducedꢀinꢀtheꢀsystem.ꢀ ꢀ
2
,ꢀ didꢀ notꢀ affectꢀ theꢀ typesꢀ ofꢀ value‐addedꢀ compoundsꢀ
O
2 2
2

ꢀ
1
OH radicalꢀ quantity,ꢀ O2ꢀ probablyꢀ wasꢀ asꢀ theꢀ mainꢀ ROSꢀ thatꢀ
attackꢀtheꢀ1°‐CꢀatomꢀofꢀDHAꢀtoꢀformꢀHPAꢀ[46].ꢀ ꢀ
Toꢀproveꢀthisꢀhypothesis,ꢀanꢀadditionalꢀexperimentꢀwasꢀcar‐
Inꢀanyꢀevent,ꢀaꢀglycerolꢀconversionꢀrouteꢀcanꢀbeꢀproposedꢀ
withꢀtheꢀpathwaysꢀpossibleꢀforꢀthisꢀsystemꢀasꢀdemonstratedꢀinꢀ
Schemeꢀ1.ꢀTheꢀthresholdꢀquantityꢀofꢀROSꢀthatꢀcontrolsꢀwhichꢀ
routeꢀofꢀglycerolꢀconversionꢀtoꢀformꢀtheꢀdifferentꢀvalue‐addedꢀ
riedꢀ outꢀ withꢀ aꢀ lowꢀ H
demonstratedꢀinꢀFig.ꢀ5,ꢀbothꢀOH radicalꢀandꢀ O
eratedꢀinꢀtheꢀpresenceꢀofꢀbothꢀlowꢀandꢀhighꢀH
tionsꢀbutꢀinꢀdifferentꢀquantitiesꢀasꢀshownꢀbyꢀtheꢀdifferentꢀde‐
creasesꢀ ofꢀ pCBAꢀ andꢀ FFAꢀ concentrations.ꢀ Largeꢀ quantitiesꢀ ofꢀ
2
O2ꢀ concentrationꢀ (0.075ꢀ mol/L).ꢀ Asꢀ

ꢀ
1
2
ꢀwereꢀstillꢀgen‐
ꢀconcentra‐
2 2
O
compoundsꢀ inꢀ theꢀ TiO ‐catalyzedꢀ photocatalyticꢀ oxidationꢀ
2
cannotꢀ beꢀ determinedꢀ atꢀ thisꢀ stage.ꢀ Moreꢀ extensiveꢀ andꢀ ex‐
pandedꢀstudiesꢀwillꢀbeꢀcarriedꢀoutꢀtoꢀdetermineꢀtheꢀthresholdꢀ
quantityꢀofꢀtheꢀROS.ꢀTheꢀresultsꢀwillꢀbeꢀreportedꢀinꢀtheꢀfuture.ꢀ
ROSꢀwereꢀproducedꢀinꢀtheꢀpresenceꢀofꢀaꢀhighꢀH
tion.ꢀ
2
O ꢀconcentra‐
2
Inꢀ theꢀ glycerolꢀ conversionꢀ andꢀ yieldꢀ ofꢀ value‐addedꢀ com‐

1980ꢀ
TrinꢀJedsukontornꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1975–1981ꢀ
Acknowledgmentsꢀ
TheꢀauthorsꢀwouldꢀlikeꢀtoꢀthankꢀtheꢀChulalongkornꢀUniver‐
sityꢀDutsadiꢀPhiphatꢀScholarship,ꢀtheꢀRatchadapisekꢀSompochꢀ
EndowmentꢀFundꢀ(Sci‐SuperꢀIIꢀGF_58_08_23_01),ꢀtheꢀThailandꢀ
ResearchꢀFundꢀ(IRG5780001)ꢀforꢀfinancialꢀsupport.ꢀ
O
OH
Referencesꢀ
OH
GCOA (C2H4O3)
[
1] H.ꢀUeoka,ꢀT.ꢀKatayama,ꢀUSꢀPatentꢀ6ꢀ288ꢀ287,ꢀ2001.ꢀ
2] J.ꢀFtouni,ꢀN.ꢀVillandier,ꢀF.ꢀAuneau,ꢀM.ꢀBesson,ꢀL.ꢀDjakovitch,ꢀC.ꢀPi‐
nel, Catal.ꢀToday,ꢀ2015,ꢀ257,ꢀ267–273.ꢀ
[
Schemeꢀ 1.ꢀ Proposedꢀ reactionꢀ pathwaysꢀ forꢀ glycerolꢀ conversionꢀ over
TiO ꢀcatalystꢀinꢀtheꢀpresenceꢀofꢀH ꢀandꢀO ꢀasꢀelectronꢀacceptors.ꢀ
[
[
[
[
[
[
[
3] G.ꢀY.ꢀYang,ꢀY.ꢀH.ꢀKe,ꢀH.ꢀF.ꢀRen,ꢀC.ꢀL.ꢀLiu,ꢀR.ꢀZ.ꢀYang,ꢀW.ꢀS.ꢀDong,ꢀChem.ꢀ
2
O
2 2
2
Eng.ꢀJ.,ꢀ2016,ꢀ283,ꢀ759–767.ꢀ ꢀ
4] H.ꢀX.ꢀYin,ꢀC.ꢀH.ꢀZhang,ꢀH.ꢀB.ꢀYin,ꢀD.ꢀZ.ꢀGao,ꢀL.ꢀQ.ꢀShen,ꢀA.ꢀL.ꢀWang,ꢀ
Chem.ꢀEng.ꢀJ.,ꢀ2016,ꢀ288,ꢀ332–343.ꢀ
5] S.ꢀThanasilp,ꢀJ.ꢀW.ꢀSchwank,ꢀV.ꢀMeeyoo,ꢀS.ꢀPengpanich,ꢀM.ꢀHunsom,ꢀ
Chem.ꢀEng.ꢀJ.,ꢀ2015,ꢀ275,ꢀ113–124.ꢀ
6] S.ꢀThanasilp,ꢀJ.ꢀW.ꢀSchwank,ꢀV.ꢀMeeyoo,ꢀS.ꢀPengpanich,ꢀM.ꢀHunsom,ꢀ
J.ꢀMol.ꢀCatal.ꢀA,ꢀ2013,ꢀ380,ꢀ49–56.ꢀ
4.ꢀ ꢀ Conclusionsꢀ
Twoꢀ typesꢀ ofꢀ chemicalꢀ agents,ꢀ namely,ꢀ H
2
O
2
ꢀ andꢀ O ,ꢀ wereꢀ
2
usedꢀasꢀtheꢀelectronꢀacceptorꢀforꢀtheꢀphotocatalyticꢀoxidationꢀofꢀ

glycerolꢀ withꢀ TiO
2
ꢀ atꢀ ambientꢀ conditions.ꢀ HO ꢀ radicalsꢀ wereꢀ
7] K.ꢀ Omata,ꢀ K.ꢀ Matsumoto,ꢀ T.ꢀ Murayama,ꢀ W.ꢀ Ueda,ꢀ Catal.ꢀ Today,ꢀ
generatedꢀ inꢀ theꢀ systemꢀ havingꢀ irradiatedꢀ UVꢀ lightꢀ andꢀ TiO2ꢀ
bothꢀinꢀtheꢀabsenceꢀandꢀpresenceꢀofꢀanꢀelectronꢀacceptor,ꢀwhileꢀ
2016,ꢀ259,ꢀ205–212.ꢀ
8] R.ꢀCiriminna,ꢀG.ꢀPalmisano,ꢀC.ꢀD.ꢀPina,ꢀM.ꢀRossi,ꢀM.ꢀPagliaro,ꢀTetra‐
hedronꢀLett.,ꢀ2006,ꢀ47,ꢀ6993–6995.ꢀ ꢀ
9] J.ꢀLuo,ꢀH.ꢀG.ꢀLi,ꢀN.ꢀZhao,ꢀF.ꢀWang,ꢀF.ꢀK.ꢀXiao,ꢀJ.ꢀFuelꢀChem.ꢀTechnol.,ꢀ
1O
2
ꢀ canꢀ onlyꢀ beꢀ producedꢀ inꢀ theꢀ systemꢀ withꢀ anꢀ electronꢀ ac‐
ceptor.ꢀTheꢀuseꢀofꢀbothꢀchemicalsꢀasꢀtheꢀelectronꢀacceptorꢀen‐

ꢀ
1
2
hancedꢀtheꢀgenerationꢀofꢀbothꢀOH radicalsꢀandꢀ O .ꢀTheꢀtypesꢀ
2015,ꢀ43,ꢀ677–683.ꢀ
ofꢀ productꢀ compoundsꢀ wereꢀ notꢀ affectedꢀ byꢀ theꢀ typeꢀ ofꢀ ROSꢀ
generatedꢀinꢀtheꢀsystemꢀbutꢀwasꢀaffectedꢀbyꢀtheꢀROSꢀconcen‐
tration.ꢀAtꢀleastꢀfourꢀcompounds,ꢀnamely,ꢀDHA,ꢀGCA,ꢀGCD,ꢀandꢀ
GCOA,ꢀwereꢀproducedꢀinꢀtheꢀphotocatalyticꢀoxidationꢀofꢀglycer‐
[
10] P.ꢀ K.ꢀ Dikshit,ꢀ V.ꢀ S.ꢀ Moholkar,ꢀ Bioresour.ꢀ Technol.,ꢀ 2016,ꢀ 216,ꢀ
1058–1065.
[11] X.ꢀM.ꢀNing,ꢀY.ꢀH.ꢀLi,ꢀH.ꢀYu,ꢀF.ꢀPeng,ꢀH.ꢀJ.ꢀWang,ꢀY.ꢀH.ꢀYang,ꢀJ.ꢀCatal.,ꢀ
2016,ꢀ335,ꢀ95–104.ꢀ
[12] R.ꢀ Estevez,ꢀ S.ꢀ Lopez‐Pedrajas,ꢀ F.ꢀ Blanco‐Bonilla,ꢀ D.ꢀ Luna,ꢀ F.ꢀ M.ꢀ
Bautista,ꢀChem.ꢀEng.ꢀJ.,ꢀ2015,ꢀ282,ꢀ179–186.ꢀ
olꢀbyꢀTiO ꢀinꢀtheꢀpresenceꢀofꢀROSꢀinꢀbothꢀlowꢀandꢀhighꢀconcen‐
2
trations,ꢀwhileꢀHPAꢀandꢀFMDꢀwereꢀproducedꢀonlyꢀatꢀlowꢀROSꢀ
concentration.ꢀ
[13] C.ꢀGarcía‐Sancho,ꢀJ.ꢀA.ꢀCecilia,ꢀA.ꢀMoreno‐Ruiz,ꢀJ.ꢀM.ꢀMérida‐Robles,ꢀ
ꢀ
GraphicalꢀAbstractꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2016,ꢀ37:ꢀ1975–1981ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(16)62519‐6

1
EffectꢀofꢀelectronꢀacceptorsꢀH
oxidationꢀofꢀglycerolꢀ
2
O
2
ꢀandꢀO
2
ꢀonꢀtheꢀgeneratedꢀreactiveꢀoxygenꢀspeciesꢀ O
2
ꢀandꢀOH ꢀinꢀTiO ‐catalyzedꢀphotocatalyticꢀ
2
ꢀ
TrinꢀJedsukontorn,ꢀVissanuꢀMeeyoo,ꢀNagahiroꢀSaito,ꢀMaliꢀHunsom*ꢀ
ChulalongkornꢀUniversity,ꢀThailand;ꢀMahanakornꢀUniversityꢀofꢀTechnology,ꢀThailand;ꢀNagoyaꢀUniversity,ꢀJapanꢀ ꢀ
Light
O2
-
- -
O2
-
H O
2
H O
2
OH
1O2
O
+
+ +
OH
OH
OH
GCOA (C2H4O3)
ꢀ
Theꢀeffectꢀofꢀtheꢀelectronꢀacceptorꢀ(O
2
ꢀorꢀH
2
O
2
)ꢀonꢀtheꢀphotocatalyticꢀoxidationꢀofꢀglycerolꢀbyꢀTiO
2
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