光电化学课件-表面催化转移

光催化：光→半导体→氧化还原反应co-catalystco-catalystVBCB－+O2/H2ONHE(pH=7)H+/H2CO2/CH4CO2/COCO2/CH3OHCO2C1&C2H2OO2H2H+H2OO2e-h+CO2/CO2••-CO2/HCHOsemiconductor•太阳光的吸收•光生电荷分离•光生电荷转移Ƞ光催化=Ƞ光吸收×Ƞ电荷分离×Ƞ电荷转移主要内容表面原子结构与晶面控制助催化剂晶面控制单体光催化材料TiO2{101}、{001}原子结构特定晶面选择性暴露•表面电荷转移•反应物分子吸附•界面结构整体红移(101)：50%Ti5c+50%Ti6c(001)：100%Ti5c异质结构光催化材料无特定晶面含特定晶面高能晶面（晶体生长中会快速消失）的控制制备是关键。单体光催化材料异质结构光催化材料20081972F.DeAngelis,andetal.J.Phys.Chem.C2012,116,18124.不同晶面上的染料分子吸附构建晶面：后期切割Pastewkaetal.NatureMater.2011,10,34.构建晶面：晶体生长控制溶剂种类溶质种类异质原子反应温度晶体生长三大“定律”：1.总表面能趋于最小化；2.表面能越高，生长速率越大；3.生长速率越大的晶面,终态中所占比例越少。调控表面能大小顺序可改变晶面所占比例Zhangetal.J.Am.Chem.Soc.2007,129,13520.G.Liu,etal.Chem.Commun.2011,47,6763.(featurearticle)关于锐钛矿TiO2{001}(101)(101)(001)表面能:{001}{101}0.90.44Jm-2如何使得表面能{001}{101}？Phys.Rev.Lett.1998,81,2954.理论预测TiO2{001}表面可实现水分子的自动分解，是高活性面。高比例{001}TiO2的制备001HGYang,CSun,SQiao,GQLu,etal.Nature2008.表面Ti-F键可逆转{001}、{101}表面能大小顺序；TiF4+HF→TiO2withlarge{001}高比例{001}TiO2的制备R.Menzel,andetal.Chem.Mater.2013,25,2137H.G.Yang,andetal.Chem.Commun.2011,47,4400.98.7%{001}and1.3%{010}500nm{001}500nm1µmd250nm含特定晶面TiO2晶体的制备Anatase(010)Rutile(110)/(111)Rutile(111)Anatase(101)(101)/(001)Anatase(001)Anatase(301)酸性••••••••••••中性••••••••••••碱性表面能：{001}(0.90Jm-2){010}(0.53Jm-2){101}(0.43Jm-2)Barnard,etal.NanoLett.,2005,5,1261{101}:94%;{001}:6%.Lazzeri,etal.Phys.Rev.B2001,63,155409.关于锐钛矿TiO2{010}H2generationOHradical富含不同晶面的TiO2晶面控制Ti(SO4)2+HFTiO2---{001},{101},{010}.光催化活性•F钝化后的各晶面活性相近；•去F后，晶体活性顺序为{010}{101}{001}.AngewChemIntEd2011.晶面原子结构与晶面电子结构协同决定晶体的光催化活性100%Ti5c50%Ti5c+50%Ti6c100%Ti5c富含不同晶面的TiO2晶面控制F-可有效降低高能面表面能•HF高毒性；•去F过程可能会带来不可预见的表面结构变化。•晶体生长取向性团聚•弱碱性调控表面能•基体晶格匹配控制晶化500nm{001}1µmd500nm250nmAnataseAnataseRutileRutile晶面控制无氟形貌控制剂制备高能面02468100510152025P25[CH4]/µmolg-1Irradiationtime/hnanorodswith{010}ChemCommun2011,47,8361.Cs0.68Ti1.83O4+H2O→TiO2+CsOHDSSCReductionofCO2弱碱性晶面控制无氟形貌控制剂制备高能面晶面控制晶格匹配控制AmorphousTiO2film→RutileTiO2withdefinedfacetsNanoscale2012,4,3871.无氟形貌控制剂制备高能面15µm2µm15µm晶面控制250nm250nm无氟形貌控制剂制备高能面晶面控制无氟形貌控制剂制备高能面取向性团聚控制：降低表面能无氟形貌控制剂制备高能面500nm{001}BoronrichBoronfreeheatingAdv.Funct.Mater.2012,22,3233.晶面控制无氟、无形貌控制剂制备高能面晶面控制B2-+Ti4+→B3++Ti3+468464460456452afterheatingTi3+Intensity/a.u.Bindingenergy/eVTi2pbeforeheatingTi3dO2pTi3dO2pEredox0/Vvs.NHE(i)(ii)Eg=3.22eV3.22eVH+/H20VO2/H2O1.23V△=0.26eV△=0.26eV(i)(ii)CBVBCBVBBrichBfreeBfreesurfaceBcontainedsurfaceTi3+诱导的带弯效应强还原能力强氧化能力F.Amano,andetal.,Chem.Mater.2009,21,2601.F.E.Oropeza,andetal.,Cryst.GrowthDes.2013,13,1438.晶面控制TiCl4+O2→TiO2with{001}高温气相氧化SrTiO3(001)上外延生长晶面控制High-indexfacetsH.G.Yangandetal.Angew.Chem.Int.Ed.2011,50,3764.；H.G.Yangandetal.NatureCommun.2014,ASAP.晶面控制E.J.W.Crossland,andetal.Nature2013,495,215.Facetedmesoporousanatasesinglecrystals-0.6-0.30.00.30.60.90.000.040.080.120.160.20offCurrentdensity/mAcm-2Appliedbiasvs.Ag/AgCl/VSolidsinglecrystalMesoporoussinglecrystalonMesoporoussinglecrystalrutileTiO22μm1μmde200nm100nmbcaSeededmesoporoussilicatemplateSeedednucleationofTiO2crystalsintemplatepores(111)(110)Etchsilica(110)(111)(111)(110)50nmabc2nm0000011-10Chem.Commun.2013,49,11770.晶面控制Facetedmesoporousrutilesinglecrystals5µm(101)(001)NdopedTiO2TiNTiO2-xNxTiS2TiO2-xSxTiB2TiO2-xBxTiB2TiO2-xHFhydrothermalG.Liu,etal.J.Am.Chem.Soc.2009J.Phys.Chem.C2009Adv.Funct.Mater.2012TiX(X=nonmentaldopant)掺杂&晶面“氧化钛和掺杂剂前驱体合二为一”TiF4/TiCl4/TiCl3/TTIP/Ti(SO4)2+含掺杂原子原料dopedTiO2常规晶面控制(101)(101)(001)(1)晶面控制(2)缺陷控制表面结构控制Nowotnyetal.JPhysChemC2008Bikondoaetal.NatMater2006DissociativeadsorptionofH2OonoxygenvacanciesofTiO2LoweredreactionbarrierofH2OsplittingreactiononTivacanciesofTiO2•Variousdefects(i.e.,Ovacancies,Tivacancies,interstitialTiatomsinTiO2)existingonoxidesurface•Surfacedefectsactingasactiveadsorptionsitesofreactants•Loweringreactionbarriers•Introducingstabledefectsisaneffectivemethodofimprovingphotocatalyticactivity缺陷控制(001)(101)0204060801001200102030405060TiO2Intensity@426nm/a.u.Irradiationtime/minTiO2withOVs0204060801001200.00.20.40.60.81.0TiO2TiO2withOVsIrradiationtime/minTiB2(metallic)TiO2-x+releasedH2+by-productcontainingBHFG.Liuetal,JPhysChemC2009UV-visiblelightVisiblelightOxygendeficientanataseTiO2•Improvedphotocatalytichydrogenevolutionbyafactorof1.7underUV;•Noactivityundervisiblelight.缺陷控制ChemCommun2013,49,6191.Heatinginair:stoichiometricrutileTiO2filmonTisubstrateHeatinginAr:nonstoichiometricrutileTiO2-xfilmonTisubstrate(TiO2+Ti→TiO2-x)TiNonstoichiometricrutileTiO2electrodes缺陷控制Aconcentrationof15at%oxygenvacanciesinthebulknonstoichiometricstoichiometric•OxygenvacancyimprovingPECwatersplittingactivityby1.7timesunderUV-visiblelightDepthdependentratioofOtoTiPECwatersplittingofTiO2photoanodes缺陷控制StoichiometricTiO2RCT=1430Ω(Interfacialchargetransferresistance)Re=5.5Ω(electroderesistance)NonstoichiometricTiO2RCT1=573Ω;RCT2=26ΩRe=4.9Ωstoichiometricnonstoichiometric•twotypesofinterfacialchargetransferprocesses•remarkablyloweringRCT•LoweringelectroderesistanceOxygenvacanciesthroughoutthebulkofTiO2Characteristicsofinterfacechargetransfers缺陷控制-1.0-0.8-0.6-0.4-0.20.00E+0002.00E+0104.00E+0106.00E+0108.00E+0101.00E