XAFS应用介绍.ppt

X射线吸收精细结构谱XAFS（实验方法和应用）,WebofScienceSearch:“EXAFS”or“XAFS”(butnot“XAS”toomanyfalsehits)1971-1975:8PublicationsLastyear:743PublicationsLast10years:7,199Publications,XAFSBeamlineDesignParameter,位于第三代上海同步辐射装置的BL14W1是一个高性能的X射线吸收谱光束线站。在一期的七条光束线站中BL14W1设计为通用吸收谱线站。BL14W1的光源是一个38极Wiggler插入件，最大磁场为1.2T，磁场周期为80mm.XAFS光束线的主要光学部件包括一个准直镜，一个配有Si(111)和Si(311)的液氮冷却双晶单色器，一个聚焦镜，一个高次谐波抑制镜。光束线有聚焦和非聚焦两种工作模式，其中，聚焦模式下能量范围为422.5keV，非聚焦模式下的能量范围为3.550keV。,国内外同类线站性能比较,ExperimentalStation,PotentialcapabilityMinimumDetectionLimit1ppm,ItisageneralandhighperformanceXAFSbeamline,withhighflux、highsignal/noiseratioandfastdatacollection.,XAFSanalyticaltechniquesatSSRF,32元高纯Ge探测器及XIA电子学系统4元Si漂移探测器及采集系统Lytle荧光电离室Oxford电离室五维样品台掠入射平台低温样品室(4K)和高温炉,XAFS线站主要仪器设备,XAFS线站主要实验技术,透射XAFS（TransmissionXAFS）荧光XAFS（FluoresceXAFS）掠入射XAFS（GrazingIncidentXAFS）原位XAFS（InsituXAFS）快速XAFS(QXAFS),ConventionalXAFSandQXAFSspectra(5Sec)ofCufoilatKedgemeasuredatBL14W1beamlineincomparisonwithstandardXAFSspectra(thedataisfromChicagoUniversityXAFSlibrary,whichwasmeasuredinAPS13ID),comparisonwithAPSstandardXAFSspectra,SR-XAFS实验框图,XAFS在钙钛矿催化剂研究中的应用,汽车尾气污染问题严重,汽车尾气的污染物，CO、HC以及NOx等，严重威胁到人类的生活，对其治理受到全球范围的重视。世界上污染最为严重的二十个城市，出现频率最高的就是中国的城市，占据60%。大气污染问题与汽车尾气排放具有很高的相关性。引起的呼吸系统疾病(主要是慢性阻塞性肺病)在我国城市居民主要疾病死亡构成中占12.6%，59%以上的司机患有不同程度的呼吸道疾病国内不断提高汽车尾气排放处理标准。国内在尾气处理催化剂研究人员众多。,Mazda:Worldsfirstapplicationofsingle-nanocatalysttechnologyincatalyticconverters,Self-regenerationofaPd-perovskitecatalystforautomotiveemissionscontrol,用XAFS手段研究催化材料的重生问题，研究其反应前后的结构变化，发现其在催化反应前后所处晶格和配位环境差异，解释了其能长期保持高活性的原因。SPring-8Nature418,164-167(11July2002),Improvingcatalyticconverters,为了提高催化剂的催化效率，科学家利用同步辐射装置开展很多原位实时监测反应过程的研究。XAFS可以提供很重要的在金属催化剂反应过程中，与局域结构和电子环境有关的原位动力学信息，他的动力学行为可以在ms,us,以至于ps.fs内研究。,M.A.Newtonetal.,NatureMaterials2007,6,528-532;Angew.ChemInt.Ed.2007,45,8629-8631,Fig.99:NormalisedPdKedgeenergydispersiveEXAFSspectraderivedduringaswitchfroma5%NO/Hefeedtoa5%CO/Hefeed(both75mlmin1flow)at673Kovera1wt%Pd/10ZCAsample.Eachspectrumwasacquiredinca.250msecs.Forclarityonly1spectrum/secondisplotted.TheredtoyellowshadingisindicativeoftheswitchfromtheNOtoCOfeed.,Fig.100:Infraredspectra(averagedover9reversibleNO/COswitches)takenatthesametimeastheEXAFSspectrashowninFigure99,collectedwitha3Hzspectralacquistionspeed.Themajorgasphaseandsurfacefunctionalitiesobservedduringtheexperimentareindicated.Againtheshadingoftheflowofthegraphindicatesthechangeofreactivefeedstock.,国内的研究,汽车尾气净化装置及催化剂,通过EXAFS研究助剂Fe的添加对催化剂Pt/Ba/Al2O3中Pt物种微观结构的影响，这种微观结构的改变对催化剂组分间的作用和催化性能产生了显著影响。MengMetal.AppliedCatalysisB:Environmental78(2008)38,XAFS在电化学研究中应用,“Ethanolisoneofthemostidealreactantsforfuelcells,”saidBrookhavenchemistRadoslavAdzic.“Itseasytoproduce,renewable,nontoxic,relativelyeasytotransport,andithasahighenergydensity.Amajorhurdletothecommercialuseofdirectethanolfuelcellsisthemoleculesslow,inefficientoxidation,whichbreaksthecompoundintohydrogenionsandelectronsthatareneededtogenerateelectricity.Specifically,scientistshavebeenunabletofindacatalystcapableofbreakingthebondsbetweenethanolscarbonatoms.ButatBrookhaven,scientistshavefoundawinner.Madeofplatinumandrhodiumatomsoncarbon-supportedtindioxidenanoparticles,theresearchteamselectrocatalystiscapableofbreakingcarbonbondsatroomtemperatureandefficientlyoxidizingethanolintocarbondioxideasthemainreactionproduct.Othercatalysts,bycomparison,produceacetalhydeandaceticacidasthemainproducts,whichmakethemunsuitableforpowergeneration.,氢电池：储存、运输困难甲醇电池：CO中间物质乙醇电池：氧化困难，,“Theabilitytosplitthecarbon-carbonbondandgenerateCO2atroomtemperatureisacompletelynewfeatureofcatalysis,”Adzicsaid.“Therearenoothercatalyststhatcanachievethisatpracticalpotentials.”,ThemainabsorptionpeaksattheRhandPtedgeshaveaverysmallpotentialdependence,indicatingthatthesurfacesareonlyslightlyoxidized,unliketheprocessthatoccurswiththepureRhphase.ItislikelythatOH,whichispresentontheSnO2surfaceinaqueoussolutions,causesashiftinsurfaceoxidationofRhandPt(RhorPtOHformation),Measurementsofmetalmetal(RhPtandPtRh)coordinationnumbersNRh-PtandNPt-Rhenabledustoobtaintheaveragecompositionofthenanoparticles:x(Pt)/x(Rh)=NRh-Pt/NPt-Rh=2.1(0.3),inreasonablygoodagreementwiththeICPdatax(Pt)/x(Rh)=1.5(0.2).Theabsolutevaluesofthesecoordinationnumbersindicatethesamesizerange(13nm)asobtainedbyTEM.TheobtainedPtandRhcoordinationnumbershavesimilarvalues9.5(0.8)and10.8(0.8)respectively,consistentwithhomogeneousdistributionofPtandRhthroughouttheparticles.Inaddition,astheNPtPt/NPtRhandNRhPt/NRhRhratioswerefoundtobeconsistent,withthebulkratiosofPtandRhconcentrationsobtainedindependentlybyEXAFSandICP,weconcludethatthePtandRhformedaquasi-randomalloy.FurtherindependentevidencetowardsthatconclusionisthesimilaritybetweenthePtPt,PtRhandRhRhbondlengthsfoundbyourEXAFSanalysis:2.743,2.725,and2.705,respectively,thatis,characterizedbyamuchsmallerspreadthanbetweenpurePt(2.775)andRh(2.689).,insituIRRAStoidentifytheintermediatesandproductsofethanoloxidation,XASofPlatinumMonolayerFuelCellElectrocatalystsUnambiguous,DirectCorrelationofSpectroscopyDatawithCatalyticProperties,(a)ModelsofpseudomorphicmonolayersofPtonthreedifferentsubstratesinducingcompressivestrain(Ru(0001)andPd(111)andexpansivestrain(Au(111).(b)SchematicofPtmonolayerelectrocatalystsubjecttosynchrotronX-ray,K.Sasaki,R.R.Adzic.SynchrotronRadiatinNews,2009,22,17-21,StructuralandElectronicPropertiesofPlatinumNanoparticleSurfaceinanAqueousSystemProbedbyInSituX-rayAbsorptionSpectroscopy,其他几个与电池材料有关的例子,Dischargeofnewlithiumbatterymaterials:LixFePO4,LixFePO4cathode0.1Hz,averagedover75spectra,lithiationspeedC/3,startingwithx=0.56.OxidationstatechangesfromFe3+toFe2+.,FeK-edge,Edgeshiftatmd=0.5,LixNi0.5Mn0.5O2-cathodeMeasuredatNiK-andMnK-edgesalternatelyduringdischarge.0.1Hz,averagedover20spectra.LithiationspeedC/4.5,startingwithx=0.414.OxidationstatechangesfromNi4+overNi3+toNi2+.,Dischargeofnewlithiumbatterymaterials:LixNi0.5Mn0.5O2,NiK-edge,LixNi0.5Mn0.5O2-cathodeMeasuredatNiK-andMnK-edgesalternatelyduringdischarge.0.1Hz,averagedover20spectra.LithiationspeedC/4.5,startingwithx=0.414.SignificantchangesintheEXAFS.,Dischargeofnewlithiumbatterymaterials:LixNi0.5Mn0.5O2,NiK-edge,LixNi0.5Mn0.5O2-cathodeMeasuredatNiK-andMnK-edgesalternatelyduringdischarge.0.1Hz,averagedover20spectra.LithiationspeedC/4.5,startingwithx=0.414.OxidationstateofMnstaysinatetravalentstate.,Dischargeofnewlithiumbatterymaterials:LixNi0.5Mn0.5O2,MnK-edge,直接甲醇燃料电池DMFC,ElectrochemicalcellforinsituEXAFSoffuelcellelectrodesonstation16.5attheSRS,Daresbury,PEMfuelcellforinsituEXAFSstudiesofanodeorcathodecatalystsonstation16.5attheSRS,Daresbury.Thecelldesignenablesthestudyofrealisticcatalystloadingsof1mgPtpercm-2ofelectrodeareaandoperatesunderfullyhumidifiedconditionsat80C.,优点,缺点,时间分辨XAFS在动力学研究中应用,QXAFS-催化-Pt/Al2O3-CO-氧化,时间分辨XAFS在反应动力学应用,时间分辨XAFS在反应动力学应用,Filmingchemicalreactions,Thestudyoftransientstatesofmatterthatlastnanoseconds(10-9s),orevenpicoseconds(10-12s),isoneofthescientificchallengesthattheESRFhastakenupsuccessfully.Forexample,researchersobservedwhathappenstotheC2H4I2moleculeinwaterwhenhitbyaflashoflaserlight.Thepumpandprobetechniqueusedinthisexperimentmayalsohelpinthefuturetostudynanomaterialsandproteinsinaction.,H.Iheeetal.,Science2005,309,1223,XAFS在多相催化中应用,solidcatalyst,gases,Surfaceevents,Molecularunderstanding,Atomicscaleconstruction,Dynamicprobeofoperatingstate,在原子精度上设计、构筑高效催化剂；在分子精度上揭示反应物向产物的转化；发展表征工具，原位、实时、高空间分辨地表征工作状态催化剂，实现对催化过程本质的理解,DOEReport2007,ActivationofaCuO/ZnO/Al2O3catalyst,Catalysisformsmethanolfromsynthesisgas:CO+2H2CH3OH.Alsohydrogencanbeproducedfromsyngasviathewater-gas-shiftreaction:CO+H2OCO2+H2.CuO/ZnO-catalyst,asprepared:CuinsolidsolutionwithZnO,substitutingZn2+asCu2+.ReductionofcatalystinH2atmosphere:Cureducedtometallicstate,migratestoZnOsurfaceCuformsparticlesoffewnmsize.ClustersizeandatomicstructureiscrucialforcatalyticactivitySmallerclusterslargerspecificsurfacehigheractivitylessmaterialneeded(expensive,evennoblemetals!),AdvancingTime-resolvedMethodsinMonitoringandCharacterizationofCatalysts,ReductionofaCuO/ZnO/Al2O3methanolcatalystinH2atmosphere,observedwith50mstimeresolution.MeasurementsperformedatHASYLABincollaborationwiththegroupofB.S.Clausen.,Anovelfastmonochromator:Drivesystem,Goal:Faster(ms),widespectralrange,continuousmovement,Currentlyupto40Hzpossible80spectra/s12.5ms/spectrum,ExperimentsatAPSundulator1-ID,Monochromator,Catalyticreactor,CuO/ZnO-catalyst:Reduction,CuK-edge,Dt=200s,J.-D.GrunwaldtandA.Baiker,ETHZrich,CuO/ZnO-catalyst:Reduction,CuK-edge,Dt=200s,Tomographicabsorptionspectroscopy:Enteringthe3rddimension,m-XAFSin2Dand3D,Characterizationofmulticomponentsamplesonmm-scaleValencedistributionofelements2D-mapping:0.25mm2with5mmresolution:10.000spectranotfeasiblewithconventionalmethods,30s/scan3.5daysoscillatingQEXAFSatmoderate10Hz8min3D-Tomography:EvenmoretimeconsumingFirstexperimentsatESRF(BM)andAPS(taperedundulator)FocussingwithX-raylensesFocalsize6mmx2mm.Evendilutebiologicalsamplesinfluorescencemodepossible!,XANESm-tomography,rotation,translation,I1,I2,I0,referencesample,L2,horizontalfocalsize:6-10m,refractivelens,monochromaticX-raysfromoscillatingmonochromator,CollaborationwithRWTHAachen(B.Lengeler)andTUDresden(C.Schroer),X-rayAbsorptionSpectroscopicMicroscopy:FromtheMicro-totheNanoscale,XANEStomography:(a)schematicsketchofthesample.(b)TomographicreconstructionofthesampleonavirtualsectionatX-rayenergyE=8995eV.Fromthetomographicdataset,thefullXANESspectraateachlocationonthevirtualsectioncanbereconstructed.Twoexamplespectraforlocationsshownin(b)aredepictedin(c).(d)Relativeconcentrationsofmetallic,monovalent,andbivalentCuinsidetheglasscapillary.Theconcentrationofbivalentcopperisbelowthedetectionlimitofthemethod.AttenuationgeneratedbyelementsotherthanCuisshowninthelowerrightimage.,MeasuredData,acquire10spectrain1secondsamplingrate:100kHz,102projections91pointsperprojection,Ateachpositioninthescan:,Acquisitionoftomographicdataset:,over90.000spectrawith104pointseach7GByteofrawdata,rotation,translation,Nearedgespectrum:,Sample:CuO/ZnOcatalystinglasscapillary,Cu/ZnOcatalyst,Sampleinglasscapillary,outerdiameter500mm,innerdiameter400mm.Beamsize:10mmx10mm,Samplebelow/aboveCuK-edge,Reconstructedspectrawithreferences,C.G.Schroeretal.,Appl.Phys.Lett.82,3360(2003),Reconstructionatdifferentpositionsafterseveraloxidation/reductioncycles:Whathappenstothecatalystduringcatalysis?,AllspectracanbedecomposedintocontentoftheCu-oxidesandCutoanswerthisquestion!,Cu/ZnOcatalyst:Cudistribution,CuCu(I),1.26:1,Averageoverwholecrosssection:Cu:Cu(I)=51:49,Verydetailedinsituobservationofbehaviourofrealcatalysts!,XAFS在表面有机金属化学中应用,XAFS在有机金属化学中应用-Zeolite-Ir,XAFS在双金属纳米粒子研究中应用,Magneticnanoparticles,Iron-platinumnanoparticlesareknownfortheirinterestingmagneticproperties.AttheESRF,theyweresubjectedtosuccessivetreatments.Thestructuralchangesandtheirinfluenceontheelement-specificmagneticmomentsweremonitoredbytheanalysisoftheX-rayabsorptionnear-edgestructureandtheX-raymagneticcirculardichroism.ThesynthesisedFe50Pt50particleswereself-assembledonasiliconsubstrateandexposedtoasofthydrogenplasma.Theywerethenannealedat600Cinordertoachievethechemically-orderedL10phase,C.Antoniaketal.,Phys.Rev.Lett.97,117201(2006).,NearedgeX-rayabsorptionfinestructure,C1s(C=C)*C=C：283.4eVC1s(C-H)*ring：285.2eVC1s(C-N)*ring：286.8eV,*CC,J.AM.CHEM.SOC.9VOL.131,NO.18,2009,上海光源XAFS线部分研究结果,Fe基超导材料高压X射线吸收谱结构研究,中科院物理所赵忠贤丁洪孙力玲,用于XAFS实验的金刚石,CeFeAsO1-xFx铁基超导材料结构,高压与超导临界温度关系,高压X射线吸收谱（XAFS),2008年春日本和中国科学家发现一种新型超导体铁基超导材料。铁基超导材料的发现为高温超导研究和量子凝聚物理带来了巨大的刺激和振奋，XAFS将从原子和电子结构上理解高温超导的深层机制，利用SSRF高通量、