光电化学课件-电荷分离

半导体中的激发与衰减（复合）过程SchematicphotoexcitationilidflldbSurfaceandbulkelectroncarriertrapping.inasolidfollowedbydeexcitationeventsAmyL.Linsebiglerandetal.Chem.Rev.1995,95,735.TiO2中光生电荷的探测CharacteristicEPRsignatureforphotogeneratedelectronsandholesinfullyoxidizedanataseTiO2oxidizedanataseTiO2.T.Berger,andetal.J.Phys.Chem.B2005,109,6061.基于EPR监测TiO2中光生电荷的捕获2低光照强度下捕获的光生电子、空穴浓度满足线性关系；高光照强度下捕获的光生空穴浓高光照强度下捕获的光生空穴浓度与空穴浓度偏离线性关系---由于没有足够的电子捕获态大量于没有足够的电子捕获态，大量的光生电子被激发到了导带中（EPRinactive）（EPRinactive）GhoshpetalPhysRev1969184979Berger,etal.J.Phys.Chem.B2005,109,6061.Ghoshpetal.Phys.Rev.1969,184,979.基于IR监测TiO2导带中光生电子2DiffflifdFiDiffusereflectanceinfraredFouriertransformspectraofpowderedTiO2followingUVirradiationIrradiationtimethethermallyactivatedchargeinjectionofelectronsfromtimejshallowtrapsitesintoacontinuumofstatesintheconductionbandofwide-bandconductionbandofwidebandgapsemiconductor.IRexcitationintheCBindicated.Szczepankiewicz,etal.J.Phys.Chem.B2002,106,2922.Shockley-Read-Hall捕获位复合ySchematicdiagramshowingthefourelectronictransitionprocessesthatmayoccurforthechargecarrierrecombination.Shockley,Wandetal.Phys.Rev.1952,87,835.复合动力学过程入射光强度对光诱导的分子氧脱附的影响射度对诱导的分氧脱的影分子氧的脱附速率与光强的平方根呈线性关系且光强的增加提高根呈线性关系，且光强的增加提高脱附速率。Thompson,etal.J.Phys.Chem.B2005,109,18230.复合动力学过程在低光照强度下，多数光生空穴被体相空穴捕获位捕获而无法达到表面。在高光照强度下，体相空穴捕获位多被饱和填充，使得多数空穴到达表面。Thompson,etal.J.Phys.Chem.B2005,109,18230.，，主要内容光生电荷分离、复合的基本过程光电荷分离复合的基本过程半导体中的定向电荷分离半导体中的定向电荷分离异相结中的电荷分离异相结中的电荷分离构离异质结构中的电荷分离半导体中的定向电荷分离BulkbandstructureFacedependenceofthephotocatalyticactivityofSrTiO3bymonitoringthedepositionofAgparticlesdepositionofAgparticles{100}surface{110}surface•Excitationonlyintwomarkedareas;•amomentumvectorintheΓ→XdirectionintheBrillouinzone,correspondingtoaintheBrillouinzone,correspondingtoadiffusioninthe[100]direction.ArgumentbyProf.MatthiasBatzill[100]directionisnotparallelt(110)fTop.Catal.,2007,44,529to(110)face.半导体中的定向电荷分离FerroelectricFieldFerroelectricField-+PBenedeketal.J.Phys.Chem.C2013,117,13339.半导体中的定向电荷分离BaTiO3polycrystalAg++e-→AghvSpatiallyselectivephotochemicalreductionofsilveronthesurfaceffltiBTiOBTiOofferroelectricBaTiO3Chem.Mater.2001,13,241BaTiO3singlecrystalChem.Mater.2001,13,241半导体中的定向电荷分离粒主要沉积在晶Ag颗粒主要沉积在{001}晶面Ag++e-→AghvPb2++h+H2O→PbO2hvTopCatal.2008,49,18.半导体中的定向电荷分离WithdifferentfacetsWithdifferentfacetsRutileTiORutileTiO2Agon(110)face(electronrich)PbO2on(011)face(holerich)PbO2on(011)face(holerich)AnataseTiO2A(101)f(ltih)Agon(101)face(electronrich)PbO2on(001)face(holerich)NewJ.Chem.,2002,26,1167.半导体中的定向电荷分离WithdifferentfacetsWithdifferentfacets10080100(001)(101)States4060nsityofS020Den-6-4-20246810Energy/eVG.Liuetal.Chem.Commun.2010,46,755.半导体中的定向电荷分离WithdifferentfacetsWithdifferentfacetsT.Tachikawaandetal.J.Am.Chem.Soc.2011,133,7197.半导体中的定向电荷分离WithdifferentfacetsWithdifferentfacetsT.Tachikawaandetal.J.Am.Chem.Soc.2011,133,7197.半导体中的定向电荷分离LayeredmaterialsornanosheetsLayeredmaterialsornanosheetsY.Matsumotoetal.J.Phys.Chem.C2008,112,11614半导体中的定向电荷分离LayeredmaterialsornanosheetsLayeredmaterialsornanosheetsP.NiuandG.Liuetal.Adv.Funct.Mater.2012,22,4763.主要内容光生电荷分离、复合的基本过程光电荷分离复合的基本过程半导体中的定向电荷分离半导体中的定向电荷分离异相结中的电荷分离异相结中的电荷分离构离异质结构中的电荷分离光催化材料的同素异象体Boron(B)Boron(B)α-B(3.3eV),γ-B(3.2eV),β-B(1.8eV),t-B(metallic)TiO2Anatase(32eV)rutile(30eV)brookite(33eV)Anatase(3.2eV),rutile(3.0eV),brookite(3.3eV)β-Bα-BT-Bγ-BP25TiO2中的异相结P25TiO2(Degussa,Germany)P25混相TiO2通常比单相的锐钛矿5O2(egussa,Geay)80%anatase,20%rutileSpecificsurfacearea:ca50m2g-12或金红石具有更高的光催化活性。通常认为锐钛矿的导带底比金红石Specificsurfacearea:ca50m2g1particlesize:around20nm通常认为锐矿的导带底石高0.2eV，光生电子从前者转移到后者。Ansity/a.u.AAAAAARRRRIntenR20304050602theta/degreeP25TiO2中异相结的电荷分离2种电荷分离模式两种电荷分离模式金红石TiO作为iltik金红石TiO2作为apassiveelectronsink金红石TiO2作为aelectronprovider，光生电子通过两相界面处锐钛矿的电子捕生电子通过两相界面处锐钛矿的电子捕获位转移至锐钛矿。D.C.Hurumandetal.J.Phys.Chem.B2003,107,4545.异相结中的电荷分离BandalignmentofrutileandanataseTiO2D.O.Scanlonetal.NatureMater.2013,12,798.异相结中的电荷分离BandalignmentofrutileandanataseTiO2异相结中的电荷分离ApatternedTiO(anatase)/TiO(rutile)bilayertypephotocatalyst:ApatternedTiO2(anatase)/TiO2(rutile)bilayer-typephotocatalyst:Effectoftheanatase/rutilejunctiononthephotocatalyticactivityTiO2(R)/quartzTiO2(A)/quartzTiO(A)(R)/tTiO2(A)-(R)/quartzdecompositionofCH3CHOT.Kawaharaandetal.Angew.Chem.Int.Ed.2002,41,2811.异相结中的电荷分离hvAg++e-→AghvAtsubstrateareas:AtililltitAgparticlesmainlylocatingonanatasesubstrate.BasedonactivityofindividualcomponentsBasedonactivityofindividualcomponents,Rutileitselfisphotocatalyticallyinactive.Atboundaryareas:Atboundaryareas:Agparticlesmainlylocatingonrutilepart.BasedonthedistributionofAgparticles,BasedonthedistributionofAgparticles,itwasproposedthattheelectrontransferoccursfromanatasetorutile.异相结中的电荷分离ImportanceoftherelationshipbetweensurfacephasesandphotocatalyticactivityofTiO2ofTiO2C.Li,etal.Angew.Chem.Int.Ed.2008,47,1766.异相结中的电荷分离α+βphase-junctionofGa2O3α+βphasejunctionofGa2O3X.Wangetal.Angew.Chem.Int.Ed.2012,51,13089.异相结中的电荷分离α+βphase-junctionofGaOα+βphase-junctionofGa2O3主要内容光生电荷分离、复合的基本过程光电荷分离复合的基本过程半导体中的定向电荷分离半导体中的定向电荷分