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1、,Scanning Electrochemical Microscopy扫描电化学显微镜,扫描电化学显微镜学习总结 张富纬 2016.9.17,A small probe is scanned in short distance over a sample surfaceand a characteristic property of the sample is detected.Interaction of probe and sample!其原理是在样品短距离的表面上，通过探针与样品的相互作用并检测到样品的特征属性。扫描探针技术有 STM, AFM, SNOM, SECMScanning
2、electrochemical microscopy (SECM) is the only technique able to detect(electro-) chemical reactions.SECM是唯一一种能够检测（电）化学反应的扫描探针技术。Resolution depends on the tip size!,SECM ClassificationSECM归类于扫描探针技术Scanning probe techniques:,3,Basic Setup 下图是整个仪器的形貌,4,4,这是与SECM连用的电化学工作站,这是SECM的工作池也就是放样品的区域（长宽高大概为2*2*1
3、cm）,SECM目前只能在小样品（1cm左右），平面上做一些基础性研究使用。,Imaging Modes,5,SECM的这些工作模式基底都是不通电的，这是原来理解上的一个误区。这个误区在下面反馈模式中的正反馈中给本人和万通中国的人都造成了误解。正反馈是由于基底为导体由于导体与探针之间的相互作用导致了电流的增大。 其关于电流密度的扫描是通过一定电镀时间的间隔下对被镀件表面进行扫描通过哪里沉积的多少来实现的。,Imaging Modes Negative Feedback,A reversible redox species is required !,6,Imaging Modes Positi
4、ve Feedback,7,由于基底不通电所以检测基底活性是SECM都是采用的可溶解的氧化还原电对（如Fe3+/Fe2+）。,Feedback Mode - Measurement Conditions,Calculated approach curves with RG=10 according to J. L. Amphlett et al., J. Phys. Chem. B 102 (1998), 9946,8,Feedback Mode,9,Array Scan for Surface Mapping,x,y,data point,individual line of array s
5、can,10,Feedback Mode,Visualization of electrochemical activity distribution on a sample surface.,11,Feedback Mode - Example,Ru3+Ru2+,itip,-400 mV,12,Feedback Mode - ExampleDifferences in local electrochemical activity e.g. due to surface impurities.,General goal of SECM studies is the determination
6、of the electron-transferkinetics at the sample surface!,13,Generator/Collector Mode (GC Mode),14,Generator/Collector Mode - Example,15,Comparison Feedback and GC Mode,5 mM Ru(NH3)63- in 100 mM KCl, RE: Ag/AgCl (3 M KCl), for GC: WE1: 2nd band Esample = -400 mV, WE2: 25 m Pt tip,Ru2+,Ru3+,0 mV,Ru3+,R
7、u2+,Ru3+,Ru2+,-400 mV,16,Comparison Feedback and GC Mode,5 mM Ru(NH3)63- in 100 mM KCl, RE: Ag/AgCl (3 M KCl), for GC: WE1: 2nd band Esample = -400 mV, WE2: 25 m Pt tip,+ sensitivity lateral resolution (diffusion profiles) time dependency,+ lateral resolution high background currentredox mediator re
8、quired,17,Practical Training SECM,18,Fe2+Fe3+,500 mV, Local experiments due to mobile electrochemical cell Standard EC (OCP detection, polarization curves etc.) possible Only small area of samples is in contact with electrolyte, exchangeof solution prior to each new grid point,RE,CE,ElectrolyteWE,19
9、,对于我们公司这种大且形状复杂的产品，Thomas给出了一下Cell的解决方案不过这是一种全新的技术，其液滴口直径也不超过1mm，基本无工业化应用价值。,Scanning Droplet Cell SDC,Scanning Droplet Cell Option SDC,Local experiments due to mobile electrochemical cellStandard EC (OCP detection, polarization curves etc.) possibleOnly small area of samples is in contact with elec
10、trolytePhotoelectrochemistry,RE,CE,Electrolyteinlet20,SECM ApplicationsSECM 的应用领域,Application,SECM is always useable when the local effects determine theproperty of the whole material (global appearance).SECM主要是通过研究材料的局部反应来判断材料的整体性能。,2,Fields of Application,3,腐蚀,催化剂,燃料电池,表面修饰,与我们公司关联性较大的主要就是腐蚀不过其主要是
11、用于单层涂层的耐蚀性研究。对于电镀产品而言此功能通过电化学工作站的阻抗分析也可以实现。,Reactivity on Stainless Steels 304 and 316,J. Izquierdo et al., Electrochimica Acta 134 (2014), 167,Stainless Steel 316,Stainless Steel 304,0.5 h,4h,7.5 h,24 h,0.5 h,3h,4,Distribution ofiron (II) ions0.25 M HCl(GC-Mode),O2,O2,O2,O2,O2,Corrosion of Steel Ox
12、ygen CompetitionE, iiT,EConsumption ofOxygen is traced Variation of GC-modeJ. J. Santana et al., Electrochim. Acta 55 (2010), 44885,Corrosion Protective Coatings,R. G. Duarte et al., Prog. Org. Coat. 74 (2012), 365,PVC Plastisolcoated nickel,foils and 0.5 mM,ferrocene-methanol.,Insulator as,sample s
13、urface Topography,6,Corrosion Protective Coatings,J. Izquierdo et al., Prog. Org. Coat. 74 (2012), 526,2-mercaptobenzimidazole,SECM image recordedin measuring solution of,0.1 M Na2SO4 + 1 mM,ferrocenemethanol,7,E. Martinez-Lombardia et al., Electrochim. Acta 116 (2014), 89,5 mM ferrocenemethanol,Cor
14、rosion - CopperImage with passive layerEffects due to crystallographicorientations of copperImage after removal of passive layer,8,Dissimilar Weld,J. Jayaraj et al., J. Adv. Microsc. Res. 7 (2012), 214,Tip reaction at 1.5 V:,HNO3 + 2H+ 2e- HNO2 + H2O,9,Self-healing Coatings,A. Pilbth et al., Prog. O
15、rg. Coat. 75 (2012), 480,Detection of Fe2+,Detection of O2,Microcapsules with linseed oil mixed,into epoxy resin coating.,10,Catalysis,11,Pt on C support (E-tek),Vulcan XC-72R,Printex L6,Catalysis Fuel Cells Oxygen Reduction ReactionORR in alkaline solution, effect of carbon support H2O2 detection,M
16、. H. M. T. Assumpo et al., Carbon 49 (2011), 284212,Electrocatalytic Activity of Carbon Fiber,Investigation of a single strand of carbon fiber.,3 mM -methylferrocenemethanol inphosphate buffer,Pseudo first order rateconstant via approach curvesV. S. Joshi et al., J. Phys. Chem. C 116 (2012), 970313,
17、Membrane Transport,Transport phenomena in channels / membranes / pores,14,Diffusion through Membranes for Gas Sensors,M. Nebel et al., Electrochim. Acta 55 (2010), 7923,15,Life Sciences - Biodegradable Material,M. D. Pereda et al., Acta Biomater. 6 (2010), 1772,16,Material Science Reduced Graphene O
18、xide on Fabrics,J. Molina et al., Appl. Surf. Sci. 279 (2013), 46,17,Biosensors,Biosensor characterization,18,GC and RC-SECM for Biosensors,I. Morkvenaite-Vilkonciene et al., RSC Adv. 4 (2014), 50064.,19,Cellular Activity,Release or consumption,20,Respiration Activity,d, t = 15 ms,Topography,M. Nebe
19、l et al. Angew. Chem. Int. Ed. 52 (2013) 633521,Intra- and Extracellular Redox Processes Yeast Cell,I. Morkvenaite-Vilkonciene et al., Sensors and Actuators B: Chemical 228 (2016), 200,22,SECM Advanced Detection ModesSECM 前沿的检测方法,AC-SECM 阻抗-SECM联用技术, All advantages of frequency,dependent response, N
20、o redox mediator necessary Diluted solution possible,Impedance spectra at each point of the scanned grid,measured at the tip in close distance to the sample surface.,2,AC-SECM,RE,CE,non-conductive,B. Ballesteros Katemann, A. Schulte, E. J. Calvo, M. Koudelka-Hep, W. Schuhmann, Electrochem. Commun. (
21、2002), 4 134,A. S. Baranski, P. M. Diakowski, J. Solid State Electrochem. (2004), 8, 683K. Eckhard, T. Erichsen, M. Stratmann, W. Schuhmann, Chem. Eur. J. (2008), 14, 3968,RCt,Cdl,RS,RCt,Cdl,RS,RSt,RSs,RP1,RP2,CP1,CP2,conductive sample,RctCdlRsRP,=,charge transfer resistancedouble layer capacitances
22、olution resistancepolarization resistance (sample),3,AC-SECM,RE,CE,RE,CE,Cdl,RS,RCt,Cdl,RS,RSt,RSs,RP1,RP2,CP1,CP2,constant,No faradayprozess,A. S. Baranski, P. M. Diakowski, J. Solid State Electrochem. (2004), 8, 683K. Eckhard, T. Erichsen, M. Stratmann, W. Schuhmann, Chem. Eur. J. (2008), 14, 3968
23、,No faradayprozess RCt,non-conductiveRS increases during approach,conductive samplealternative path through sample,4,Z/Z,AC-SECM,1 mM KCl, RE: Ag/AgCl, Ampl. 10 mV,RCt,Cdl,RS,RSt,RSP,RP1,RP2,CP1shortcut,CP2,RctCdlRsRP,=,charge transfer resistancedouble layer capacitancesolution resistancepolarizatio
24、n resistance (sample),0,8,0,1,32,Glass,0.5 kHz,GlassPlatinumPlatinum,6 kHZ0.5 kHz6 kHz,4L = d/r,5,Comparison LEIS and AC-SECMEWE,5-electrode configurationLEIS: Global AC perturbation atsample, measurement of local ACcurrent density to calculate localimpedance.,3-electrode configurationAC-SECM: AC pe
25、rturbation directly attip electrode and interactionunderneath measured, uses SECM tips(much smaller tips resolution) 6,High resolution imaging in SECM成像技术,Resolution in SECM, Tip size (ratio of the size of tip and structure) Distance between data points (step size) Working distance (contrast), Detec
26、tion mode and RG value of tip,*Ratio of overall electrode radius tothe radius of the active tip surface,2,Fe2+Fe3+,itip,500 mV,3,Resolution in SECM Effect of Tip Size,5 mM Fe(CN)64- in 100 mM KCl, RE: Ag/AgCl (3 M KCl), Etip = +500 mV, Feedback mode,25 m Pt tipIncrements: x = 12.5 m, y = 25 mWorking
27、 distance: 25 m,10 m Pt tipIncrements: x = 5 m, y = 10 mWorking distance: 10 m,4,Resolution in SECM Effect of Tip Size,Interaction area,depends on tip size,Signal averaged over tip size,5,Resolution in SECM Effect of Tip Size,25 m Pt tipIncrements: x = 12.5 m, y = 10 mWorking distance: 12.5 m5 mM Fe
28、(CN)64- in 100 mM KCl, RE: Ag/AgCl (3 M KCl), Etip = +500 mV,10 m Pt tipIncrements: x = 5 m, y = 10 mWorking distance: 5 m,6,Resolution in SECM - The Parameter Step Width,d,r,Fast experiment, no loss ofinformation.Max. of information andwell resolved graphs.No additional information BUTincrease of t
29、he exp. duration.Loss of information (dottedlines) but fast experiments.7,Resolution in SECM Effect of Step Width,5 m12.5 m,2 m50 m,10 m Pt tip, working distance 5 m, 10 m y-increment, 5 mM Fe(CN)64- in 100 mM KCl, RE: Ag/AgCl (3 M KCl), Etip = +500 mV,8,I = i / i,0,2,4,6,8,10,3210,4,L = d/r,1,2,10
30、m Pt tip,12.5 m x-increment, 10 m y-increment, 5 mM Fe(CN)64- in 100 mM KCl, RE: Ag/AgCl (3 M KCl), Etip = +500 mV,WD 25 m (5r),WD 5 m (r),Working distancedetermines contrast!,9,Resolution in SECM EC determines the resolution! The choice of the electrode size and the parameter step width(distance be
31、tween data points) is crucial.dr,The positioning system has a sufficient repeatability (bidirectional15 m stepper motors and 10 nm piezo system).,10,Comparison Feedback and GC Mode,5 mM Ru(NH3)63- in 100 mM KCl, RE: Ag/AgCl (3 M KCl), for GC: WE1: 2nd band Esample = -400 mV, WE2: 25 m Pt tip,Ru2+,Ru
32、3+,0 mV,Ru3+,Ru2+,Ru3+,Ru2+,-400 mV,11,Comparison Feedback and GC Mode,5 mM Ru(NH3)63- in 100 mM KCl, RE: Ag/AgCl (3 M KCl), for GC: WE1: 2nd band Esample = -400 mV, WE2: 25 m Pt tip,+ sensitivity lateral resolution (diffusion profiles) time dependency,+ lateral resolution high background currentred
33、ox mediator required,12,working distance depends on tip size,tip crash,Constant-Height vs. Constant-Distance Mode SECMWhen using a very small probe (sub-m),or scanning a rough sample, the distancedependency of the current signal cancause difficulties.loss of nearfield interaction,13,Constant-Height
34、Mode SECM,itip,z-position,ii,Electrochemical activity and topography influence the tip signal(data interpretation difficult).,14,Constant-Distance Mode SECM,itip,z-position,i,Tip follows topography and the tip signal represents theelectrochemical activity.,15,magnitude / mV,Requires specialvibratory
35、 SECM tips,Constant-Distance SECM Detection of shearforce interactions for current independentdistance controlPiezo element,Agitator,Detector,86420,10,200,250,350,400,300frequency / kHz,solutionsf regime,16,MAG / mV,Constant-Distance SECM Approach Curve,0,1,2,3,64,161412108,interaction range,contact
36、,bulk signalset pointshearforce,z-position / m17,Constant-Distance SECM Set Point,18,MAG / mV,Control Loop - Parameters,0,1,2,3,16141210864,contact,bulk signalset pointallowed deviationshearforceinteraction range,z-position / m19,Constant-Distance SECM Array Scan,Constant Distance, Current Signal,Co
37、nstant Distance, Topography Signal Signal,Height, Current,B. Ballesteros Katemann et al., Electrochem. Commun. 4 (2002), 13420,4D Constant-Distance Mode,Sf approach curves at each grid point,21,Constant-Distance SECM 4D SF/CD-SECM,M. Nebel et al., Anal. Chem. 82 (2010), 7842,22,Constant-Distance SEC
38、M,S. Neugebauer et al., Electroanalysis 18 (2006), 1929,23,4D SF/CD-SECM at ORR Catalysts in Microcavities,100 m,Topographyimage,Current image incompetition arrangement,tip: 1.6 m, 100 mM PBpH 7, Pt/C: w(Pt) = 20 %on Vulcan XC72 (ETEK Inc.)M. Nebel et al. Beilstein J. Nanotechnol. 5 (2014), 14124,gl
39、ass,RuO2(benchmark),Onset potential Determination via SF-SECM (OER)perovskite catalystsRuO2perovskite catalysts,glass,A. J. Botz et al., Electrochimica Acta 179 (2015), 3825,Cellular Activity,Release or consumption,26,Respiration Activity,d, t = 15 ms,Topography,M. Nebel et al. Angew. Chem. Int. Ed. 52 (2013) 633527,
