DOCSLIB.ORG

Assessment of an Ultramicroelectrode Array (UMEA) Sensor for The

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Assessment of an Ultramicroelectrode Array (UMEA) Sensor for The Assessmentofanultramicroelectrodearray(UMEA)sensorfor thedeterminationoftraceconcentrationsofheavymetalsinwater ZurErlangungdesakademischenGradeseines DoktorsderNaturwissenschaften anderFakultätfürBauingenieur-,Geo-undUmweltwissenschaften der UniversitätKarlsruhe genehmigte DISSERTATION von XudongXie ausVRChina 2004 TagdermündlichenPrüfung:02.06.2004 Referentin:Prof.Dr.DorisStüben Korreferent:Prof.Dr.Rolf-DieterWilken Abstract Abstract Rapid development in silicon technology and microelectronics has nowadays enabled the mass fabrication of microelectrode arrays with well-defined and reproduciblegeometriesonmicronscalesbyusingthin-filmtechnology.Comparedto conventional macroelectrodes, microelectrodes possess several attractive features, suchashighmasstransport,reducedchargingcurrent,immunitytoohmicdrop,high signal-to-noiseratio,etc.,whichareveryadvantageousfordevelopingdecentralised analyticalequipmentsintracemetalanalysis. A novel iridium-based ultramicroelectrode array chip (Ir-UMEAs) was recently designed and fabricated by means of microlithographic techniques by one of the partners (Fraunhofer Institute of Silicon Technology, ISIT, Germany) of this joint research project. The Ir-UMEA chip is made up of 4048 individual ultramicroelectrodes (working electrodes) arranged in four separate arrays. Each arrayconsistsof46x22=1012discshapedmicroelectrodeswithadiameterof1.8 µmeach,givingatotalelectrodeareaof2575µm².Theelectrodesarerecessedby 0.2µmandarespacedwithaninterelectrodedistanceof25µm. Thisstudyismainlyaimedat(i)investigatingtheelectrochemicalbehaviorandthe analytical performance of the Ir-UMEAs, (ii) assessing the analytical parameters of square-wave stripping voltammetric measurements (SWASV) using the Ir-UMEAs, and(iii)estimatingthepotentialoftheIr-UMEAsforthedevelopmentofananalytical instrument to determine trace metal concentrations in natural waters. Surface analyticaltechniques(SEM,ESEM,andAFM)showedthattheIr-UMEAchipsareof high quality, without evident defects in manufacture. Cyclic voltammetric and chronoamperometricexperimentsprovedthattheelectrochemicalbehavioroftheIr- UMEAs is dominated by features characteristic for microelectrodes (sigmoidal voltammograms, steady-state current response, etc.). The quality of the Hg-film proved to be crucial in achieving a high analytical performance. Chronocoulometry wasfoundtobethemostsuitablemethodingeneratingaHg-filmofgoodquality.An Ir-UMEA chip could be plated at least ten times without obvious loss in analytical performance, corresponding to approximately 500 measurements of trace metal i Abstract concentrationsinsyntheticaqueoussolutions.UsingSWASV,detectionlimitsof<0,1 µg/lcouldbeobtainedforthemetalsinvestigated (Cu, Pb, Cd, Zn). Precision and accuracywerefoundtobesatisfactory(about±10%ofRSD).Thoughfoulingofthe arrays with time may become a problem, an ultrasonic bath proved to be very efficient in cleaning the surface of the electrodes in laboratory. Instrumental parameters, experimental conditions, and possible interferences were investigated and optimised. Interferences due to dissolved organic matter and/or intermetallic compoundsweresignificantlyreducedbymeansofmediumexchangeandstandard addition.TheresultsobtainedwiththeIr-UMEAsensorshowedareasonablygood agreementwithhighresolutionICP-MSanalyses,indicatingthatthecombinationof microelectrodearrayswithSWASVhasagreatpotentialindevelopingamarketable fieldanalyticalsystemforthedeterminationofheavymetalconcentrationsinnatural waters. However, for in situ and on-site measurements, the protection of the UMEAs from fouling(e.g.,theintegratingofthearraysinananti-foulingmembrane)seemstobe inevitable.Inordertoavoidtheshieldeffectcausedbytheoverlappingofdiffusion layers of the individual electrodes and thus to achieve a pure microelectrode behavior with the Ir-UMEAs, increasing the ratio of interelectrode distance to electrodediameterisrecommendedforfurtherdevelopments. ii Acknowledgments Acknowledgments IwouldliketothankProf.Dr.DorisStübenforgivingmetheopportunitytomakemy PhDstudyattheInstituteofMineralogyandGeochemistry(IMG).Withoutherhelp the completion of this dissertation would not have been possible and my stay in Germanywouldnotbesofruitful.IwouldalsoliketoexpressmythankstoProf.Dr. Rolf-DieterWilkenfortakingontheroleofKorreferat. ManythanksgotoDr.ZsoltBernerforhisunselfishsupportduringthecourseofthis work.Hisvaluablesuggestion,criticalreviewofthethesis,andkindlyencouragement areveryhelpful. SpecialthanksgotoDr.StefanNorraforhishelpinusingGeographicInformation System(GIS,ArcView)andMapInfoprogrammes;Ms.ClaudiaMößnerforhereffort in ICP-MS analysis; Mr. Peter Schaup for his various technical assistance; Dr. Gerhard Ott for solving computer problems; and Ms. Gesine Preuß for the preparationoflaboratorywork. Iamgratefultothefollowingcolleaguesfortheirvarioushelps:Prof.Heinz-Günter Stosch,PD.Dr.ThomasNeumann,PD.Dr.Jörg-DetlefEckhardt,AndreaStögbauer, Ms. Rosemarie Bender, Dr. Utz Kramar, Ms. Nytz Halina, Ms. Maria Tannhäuser, HassanAboughalma,andMichaelLaueretc.. In a word, I thank all the peoples who have provided me helps during the past several years. Because of their helps, I have spent a very special and nice time. Theirhospitabilitywillstayinmymemoryforever. Finally,Iwishtoexpressmygratitudetomyfamily:myparents,YunXie&Yuzhen Zang; my wife, Cuiling; and my son, Kaibo, who have given me a lot of love, encouragement,understandings,andenergies. Thankstoallofyou iii TableofContents TableofContents Abstract........................................................................................................................ i Acknowledgments.......................................................................................................iii Contents..................................................................................................................... iv ListofFigures ............................................................................................................vii ListofTables.............................................................................................................. ix ListofAppendices...................................................................................................... ix Abbreviations .............................................................................................................iix 1.Introduction .......................................................................................................... 1 2.Reviewofresearch ...............................................................................................3 2.1Developmentofmicroelectrodes ....................................................................... 3 2.2Applicationsofmicroelectrodesinthedeterminationoftracemetals ................6 2.2.1Voltammetricsensor ................................................................................... 7 2.2.2Potentiometricsensor ................................................................................. 8 2.2.3Insitusensor...............................................................................................9 3.Theory..................................................................................................................12 3.1Electrochemicalmethods ................................................................................ 12 3.1.1Electrochemicalcell .................................................................................. 12 3.1.2Strippinganalysis......................................................................................13 3.1.2.1Anodicstrippingvoltammetry(ASV)...................................................13 3.1.2.2Potentiometricstrippinganalysis(PSA) .............................................15 3.1.3Cyclicvoltammetry(CV) ........................................................................... 16 3.1.4Chronoamperometry(CA).........................................................................18 3.1.5Squarewavetechnique ............................................................................ 18 3.2Theoryofmicroelectrodes ............................................................................... 20 3.2.1Definitionofmicroelectrodes..................................................................... 20 3.2.2Microelectrodetypes................................................................................. 21 3.2.3Advantageouspropertiesofmicroelectrodes............................................22 3.2.3.1Masstransport.................................................................................... 22 3.2.3.2Reducedchargingcurrent ..................................................................25 3.2.3.3Ohmiceffect ....................................................................................... 26 iv TableofContents 4.Fabricationofultramicroelectrodearrays ........................................................27 4.1Introduction......................................................................................................27 4.2.FabricationofUMEAs.....................................................................................28 4.2.1Design.......................................................................................................28 4.2.2Processing ................................................................................................29 4.2.3Assemblyandpackaging .......................................................................... 31 5.Characterizationofultramicroelectrodearrays................................................31
Load more

Recommended publications
  • Hydrodynamic Voltammetry As a Rapid and Simple Method for Evaluating Soil Enzyme Activities
    Sensors 2015, 15, 5331-5343; doi:10.3390/s150305331 OPEN ACCESS sensors ISSN 1424-8220 www.mdpi.com/journal/sensors Article Hydrodynamic Voltammetry as a Rapid and Simple Method for Evaluating Soil Enzyme Activities Kazuto Sazawa 1,* and Hideki Kuramitz 2 1 Center for Far Eastern Studies, University of Toyama, Gofuku 3190, 930-8555 Toyama, Japan 2 Department of Environmental Biology and Chemistry, Graduate School of Science and Engineering for Research, University of Toyama, Gofuku 3190, 930-8555 Toyama, Japan; E-Mail: [email protected] * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel./Fax: +81-76-445-66-69. Academic Editor: Ki-Hyun Kim Received: 26 December 2014 / Accepted: 28 February 2015 / Published: 4 March 2015 Abstract: Soil enzymes play essential roles in catalyzing reactions necessary for nutrient cycling in the biosphere. They are also sensitive indicators of ecosystem stress, therefore their evaluation is very important in assessing soil health and quality. The standard soil enzyme assay method based on spectroscopic detection is a complicated operation that requires the removal of soil particles. The purpose of this study was to develop a new soil enzyme assay based on hydrodynamic electrochemical detection using a rotating disk electrode in a microliter droplet. The activities of enzymes were determined by measuring the electrochemical oxidation of p-aminophenol (PAP), following the enzymatic conversion of substrate-conjugated PAP. The calibration curves of β-galactosidase (β-gal), β-glucosidase (β-glu) and acid phosphatase (AcP) showed good linear correlation after being spiked in soils using chronoamperometry.
    [Show full text]
  • Reaction Mechanism of Electrochemical Oxidation of Coo/Co(OH)2 William Prusinski Valparaiso University
    Valparaiso University ValpoScholar Chemistry Honors Papers Department of Chemistry Spring 2016 Solar Thermal Decoupled Electrolysis: Reaction Mechanism of Electrochemical Oxidation of CoO/Co(OH)2 William Prusinski Valparaiso University Follow this and additional works at: http://scholar.valpo.edu/chem_honors Part of the Physical Sciences and Mathematics Commons Recommended Citation Prusinski, William, "Solar Thermal Decoupled Electrolysis: Reaction Mechanism of Electrochemical Oxidation of CoO/Co(OH)2" (2016). Chemistry Honors Papers. 1. http://scholar.valpo.edu/chem_honors/1 This Departmental Honors Paper/Project is brought to you for free and open access by the Department of Chemistry at ValpoScholar. It has been accepted for inclusion in Chemistry Honors Papers by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at [email protected]. William Prusinski Honors Candidacy in Chemistry: Final Report CHEM 498 Advised by Dr. Jonathan Schoer Solar Thermal Decoupled Electrolysis: Reaction Mechanism of Electrochemical Oxidation of CoO/Co(OH)2 College of Arts and Sciences Valparaiso University Spring 2016 Prusinski 1 Abstract A modified water electrolysis process has been developed to produce H2. The electrolysis cell oxidizes CoO to CoOOH and Co3O4 at the anode to decrease the amount of electric work needed to reduce water to H2. The reaction mechanism through which CoO becomes oxidized was investigated, and it was observed that the electron transfer occurred through both a species present in solution and a species adsorbed to the electrode surface. A preliminary mathematical model was established based only on the electron transfer to species in solution, and several kinetic parameters of the reaction were calculated.
    [Show full text]
  • Using Chronoamperometry to Rapidly Measure and Quantitatively Analyse Rate- Performance in Battery Electrodes
    Using chronoamperometry to rapidly measure and quantitatively analyse rate- performance in battery electrodes Ruiyuan Tian,1,2 Paul J. King,3 Joao Coelho,2,4 Sang-Hoon Park,2,4 Dominik V Horvath,1,2 Valeria Nicolosi,2,4 Colm O’Dwyer,2,5 Jonathan N Coleman1,2* 1School of Physics, Trinity College Dublin, Dublin 2, Ireland 2AMBER Research Center, Trinity College Dublin, Dublin 2, Ireland 3Efficient Energy Transfer Department, Bell Labs Research, Nokia, Blanchardstown Business & Technology Park, Snugborough Road, Fingal, Dublin 15, Ireland 4School of Chemistry, Trinity College Dublin, Dublin 2, Ireland 5 School of Chemistry, University College Cork, Tyndall National Institute, and Environmental Research Institute, Cork T12 YN60, Ireland *[email protected] (Jonathan N. Coleman); Tel: +353 (0) 1 8963859. ABSTRACT: For battery electrodes, measured capacity decays as charge/discharge current is increased. Such rate-performance is important from a practical perspective and is usually characterised via galvanostatic charge-discharge measurements. However, such measurements are very slow, limiting the number of rate experiments which are practical in a given project. This is a particular problem during mechanistic studies where many rate measurements are needed. Here, building on work by Heubner at al., we demonstrate chronoamperometry (CA) as a relatively fast method for measuring capacity-rate curves with hundreds of data points down to C-rates below 0.01C. While Heubner et al. reported equations to convert current transients to capacity vs. C-rate curves, we modify these equations to give capacity as a function of charge/discharge rate, R. We show that such expressions can be combined with a basic model to obtain simple equations which can fit data for both capacity vs.
    [Show full text]
  • Stationary Electrode Voltammetry and Chronoamperometry in an Alkali Metal Carbonate-Borate Melt
    AN ABSTRACT OF THE THESIS OF DARRELL GEORGE PETCOFF for the Doctor of Philosophy (Name of student) (Degree) in Analytical Chemistry presented onC (O,/97 (Major) (Date) Title: STATIONARY ELECTRODE VOLTAMMETRY AND CHRONOAMPEROMETRY IN AN ALKALI METAL CARBONATE - BORATE. MFT T Abstract approved: Redacted for Privacy- Drir. reund The electrochemistry of the lithium-potassium-sodium carbonate-borate melt was explored by voltammetry and chrono- amperometry. In support of this, a controlled-potential polarograph and associated hardware was constructed.Several different types of reference electrodes were tried before choosing a porcelain mem- brane electrode containing a silver wire immersed in a silver sulfate melt.The special porcelain compounded was used also to construct a planar gold disk electrode.The theory of stationary electrode polarography was summarized and denormalized to provide an over- all view. A new approach to the theory of the cyclic background current was also advanced. A computer program was written to facilitate data processing.In addition to providing peak potentials, currents, and n-values, the program also resolves overlapping peaks and furnishes plots of both processed and unprocessed data. Rapid-scan voltammetry was employed to explore the electro- chemical behavior of Zn, Co, Fe, Tl, Sb, As, Ni, Sn, Cd, Te, Bi, Cr, Pb, Cu, and U in the carbonate-borate melt. Most substances gave reasonably well-defined peaks with characteristic peak potentials and n-values.Metal deposition was commonly accompanied by adsorp- tion prepeaks indicative of strong adsorption, and there was also evi- dence of a preceding chemical reaction for several elements, sug- gesting decomplexation before reduction.
    [Show full text]
  • Electrochemical Instrumentation
    Electrochemical Instrumentation ______________________________________________________________________________ CH Instruments 1 Overview CH Instruments was established in 1994. Our first instrument series, the Model 600 series electrochemical analyzer/workstation, was introduced at the end of 1994. Since then, new products have been added to provide a full line of electrochemical instrumentation: Model 400A Series Time-Resolved Electrochemical Quartz Crystal Microbalance (EQCM): for electro-deposition, adsorption, and chemical and biological sensor studies. Model 600D Series Potentiostat/Galvanostat: for general purpose electrochemical measurements, such as kinetic measurements, electroanalysis, fundamental research, corrosion, and battery studies. Model 700D Series Bipotentiostat: for rotating ring-disk electrodes (RRDE) and other cases where dual channel measurements are essential. Model 800C Series Electrochemical Detector: for either single or dual channel electrochemical detection of flow cell, capillary electrophoresis and liquid chromatography, for chemical and biological sensors, and conventional electroanalysis. Model 920C Scanning Electrochemical Microscope (SECM): for electrode surface, corrosion, biological samples, solid dissolution, liquid/liquid interfaces and membranes studies. Model 1000A Series Multi-potentiostat: 8-channel potentiostat for array electrode characterization and sensor studies. It can be used for eight independent cells or for eight working electrodes in a same solution. Model 1100A Power Potentiostat/Galvanostat: for applications involving higher current and compliance voltage. Model 1200A Handheld Potentiostat/Bipotentiostat: for electroanalysis, sensor studies, and field applications. Model 1550A Pico Liter Solution Dispenser: for making high density and high accuracy solution arrays. All models are controlled by an external PC under the Windows 95/98/NT/Me/2000/XP environment. The instruments are easy to install and use. No plug-in card or other hardware is required on the PC side.
    [Show full text]
  • Emstat-Go-Description.Pdf
    z Rev. 1-2019 EmStat Go potentiostat ...............................................................................................................2 Sensor Extension module .........................................................................................................2 Sleeves in any color .................................................................................................................3 Modular design ........................................................................................................................3 Optional battery for connecting via Bluetooth ...........................................................................3 Reduce your time-to-market ....................................................................................................4 Supported techniques ..............................................................................................................4 Voltammetric techniques ......................................................................................................4 Techniques as a function of time ..........................................................................................4 Custom software options .............................................................................................................5 Specifications of general parameters ...........................................................................................6 General pretreatment............................................................................................................6
    [Show full text]
  • Walljet Electrochemistry: Quantifying Molecular Transport Through Metallopolymeric and Zirconium Phosphonate Assembled Porphyrin Square Thin Films
    4422 Langmuir 2004, 20, 4422-4429 Walljet Electrochemistry: Quantifying Molecular Transport through Metallopolymeric and Zirconium Phosphonate Assembled Porphyrin Square Thin Films Aaron M. Massari, Richard W. Gurney, Craig P. Schwartz, SonBinh T. Nguyen, and Joseph T. Hupp* Department of Chemistry and the Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113 Received January 12, 2004. In Final Form: March 7, 2004 By employing redox-active probes, condensed-phase molecular transport through nanoporous thin films can often be measured electrochemically. Certain kinds of electrode materials (e.g. conductive glass) are difficult to fabricate as rotatable disks or as ultramicroelectrodessthe configurations most often used for electrochemical permeation measurements. These limitations point to the need for a more materials- general measurement method. Herein, we report the application of walljet electrochemistry to the study of molecular transport through model metallopolymeric films on indium tin oxide electrodes. A quantitative expression is presented that describes the transport-limited current at the walljet electrode in terms of mass transport through solution and permeation through the film phase. A comparison of the film permeabilities for a series of redox probes measured using the walljet electrode and a rotating disk electrode establishes the accuracy of the walljet method, while also demonstrating similar precision for the two methods. We apply this technique to a system consisting of zirconium phosphonate assembled films of a porphyrinic molecular square. Transport through films comprising three or more layers is free from significant contributions from pinhole defects. Surprisingly, transport through films of this kind is 2-3 orders of magnitude slower than through films constructed via interfacial polymerization of nearly identical supramolecular square building blocks (Keefe; et al.
    [Show full text]
  • For Peer Review Only
    IUPAC Terminology of electrochemical methods of analysis Journal: Pure and Applied Chemistry ManuscriptFor ID PeerPAC-REC-18-01-09.R2 Review Only Manuscript Type: Recommendation Date Submitted by the 27-Feb-2019 Author: Complete List of Authors: Pingarron, José; Complutense University of Madrid, Department of Analytical Chemistry Labuda, Jan; Slovak University of Technology, Department of Analytical Chemistry Barek, Jiří ; Charles University, Faculty of Science, Department of Analytical Chemistry Brett, Christopher; Universidade de Coimbra, Departamento de Química Camões, Maria; Universidade de Lisboa, Centro de Química Estrutural Fojta, Miroslav; Akademie ved Ceské Republiky, Institute of Biophysics Hibbert, David; University of New South Wales, School of Chemistry electoanalytical chemistry, electrodes, potentiometry, amperometry, Keywords: voltammetry, coulometry, electrogravimetry, conductometry, impedimetry, spectroelectrochemistry Author-Supplied Keywords: P.O. 13757, Research Triangle Park, NC (919) 485-8700 Page 1 of 62 IUPAC 1 2 3 4 IUPAC Provisional Recommendation 5 6 7 José M. Pingarrón1, Ján Labuda2, Jiří Barek3, Christopher M.A. Brett4, Maria Filomena 8 Camões5, Miroslav Fojta6, D. Brynn Hibbert7*. 9 10 11 Terminology of electrochemical methods of analysis (IUPAC 12 Recommendations 201x) 13 14 15 16 Abstract: Recommendations are given concerning the terminology of methods used in 17 electroanalytical chemistry.For PeerFundamental Review terms in electrochemistry Only are reproduced from 18 previous PAC Recommendations, and
    [Show full text]
  • Comparison of Differential Pulse Voltammetry (DPV)— a New Method of Carbamazepine Analysis—With Fluorescence Polarization Immunoassay (FPIA)1 H
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by National Chung Hsing University Institutional Repository ISSN 10619348, Journal of Analytical Chemistry, 2011, Vol. 66, No. 4, pp. 415–420. © Pleiades Publishing, Ltd., 2011. ARTICLES Comparison of Differential Pulse Voltammetry (DPV)— a New Method of Carbamazepine Analysis—with Fluorescence 1 Polarization Immunoassay (FPIA) H. Y. Wanga, M. L. Panb, Y. L. Oliver Sub, c, S. C. Tsaia, C. H. Kaod, S. S. Sund, and W. Y. Lina, d, e a Department of Nuclear Medicine, Taichung Veterans General Hospital, Taichung, 407 Taiwan b Department of Applied Chemistry, National Chi Nan University, Nantou Hsien, 545 Taiwan c Department of Chemistry National ChungHsing University, Taichung, 402 Taiwan d College of Medicine, China Medical University, Taichung, 404 Taiwan e Institute of Radiological Science, Central Taiwan University of Science and Technology, Taichung, 406 Taiwan Received February 2, 2009; in final form, August 15, 2010 Abstract—Carbamazepine is a widely used antiepileptic drug with narrow therapeutic range. Many methods have been developed for monitoring the serum drug level. Differential pulse voltammetry (DPV), an electro chemical method advantaged by simple, inexpensive, and relatively short analysis time, has recently been developed for carbamazepine detection. We used a newly developed DPV method with glassy carbon as a working electrode to determine the carbamazepine level. The performance of DPV is compared with the widely used fluorescence polarization immunoassay (FPIA) technique in precision, accuracy, linearity and detection limit. The precision, linearity and accuracy of the DPV and FPIA techniques were comparable at most clinical used levels.
    [Show full text]
  • Developing a Stable and Selective Non-Enzymatic Electrochemical Glucose Biosensor
    Developing a Stable and Selective Non-Enzymatic Electrochemical Glucose Biosensor A Major Qualifying Project Submitted to the Faculty of Worcester Polytechnic Institute In partial fulfillment of the requirements for the Degree in Bachelor of Science In Chemical Engineering By: Zihao Li Randy Melanson Date: 04/21/2018 Project Advisor Professor Hong Susan Zhou This report represents work of WPI undergraduate students submitted to the faculty as evidence of a degree requirement. WPI routinely publishes these reports on its web site without editorial or peer review. For more information about the projects program at WPI, see http://www.wpi.edu/Academics/Projects. Abstract The goal of this Major Qualifying Project was to develop a stable and sensitive interface architecture for an easy and reusable non-enzymatic electrochemical glucose biosensor. This was achieved by changing the copper oxide nanoparticle morphology that was deposited onto a titanium oxide nanotube array. The interface architecture of the electrode was manipulated by varying the concentration of the equimolar CuSO4/H2SO4 solution from 7.8 mM to 250 mM during electrodeposition. Through SEM imaging, cyclic voltammetry scans, and chronoamperometric readings, it was determined that the biosensor interface architecture affected its overall glucose sensing capabilities. The most ideal interface architecture that resulted in the best performing electrochemical glucose biosensor was produced in an electrolyte solution of 50 mM CuSO4/H2SO4. At this concentration, the biosensor had a linear glucose sensitivity range from 0.2 to 1.0 mM glucose and had a correlation coefficient of 0.964. 1 Acknowledgements This project team would like to thank our advisor, Professor Hong Susan Zhou, for her guidance and support through the completion of this project.
    [Show full text]
  • EIS at a Rotating Disc Electrode
    Electrochemical Impedance at a rotating disk electrode Perspective and goal • Perspective: – Researcher interested in using EIS at RDEs • Basic echem understanding • Some EIS exposure • Goal: – Provide an introduction and practical framework to run EIS at RDEs. 2 Topics • Steady state mass transfer • RDE basics and the Levich equation • Nernst diffusion layer (NDL) and the porous bounded Warburg Application • Electroactive species in biofilms • Impedance behavior of electrochemically active biofilms (EAB) at an RDE 3 Why use an RDE? • Achieve the steady state mass transfer condition: • i = nFA(D/δ)(Cbulk – Csurface) • iL = nFA(D/δ)(Cbulk) where Csurface is zero – Current is limited by the mass transfer rate – Electrode potential is predicted by the Nernst equation – “steady state” = does not change with time • Difficult to achieve in a stationary system: • δ(t) ~ (Dt)1/2 – t is time elapsed after a large potential step – Derived from the Cottrell equation 4 Source: Bard and Faulkner, "Electrochemical Methods", Chapter 1, Wiley, 2001. Difficulty with stationary systems • Background convection impacts the current measurement – After t > 20s, becomes more pronounced – Thermal gradients, vibration, other external factors • The transient current behavior and background convection influence conflicts with the EIS stability requirement, especially when wanting to run EIS at a non-zero DC current • EIS generally limited to running at the open circuit potential for diffusion-limited stationary systems 5 Source: Bard and Faulkner, "Electrochemical
    [Show full text]
  • Electrochemical Behavior and Electrodeposition of Sn Coating from Choline Chloride–Urea Deep Eutectic Solvents
    coatings Article Electrochemical Behavior and Electrodeposition of Sn Coating from Choline Chloride–Urea Deep Eutectic Solvents Xiaozhou Cao 1 , Lulu Xu 1, Chao Wang 2, Siyi Li 1, Dong Wu 3, Yuanyuan Shi 4, Fengguo Liu 1 and Xiangxin Xue 1,* 1 School of Metallurgy, Northeastern University, Shenyang 110819, China; [email protected] (X.C.); [email protected] (L.X.); [email protected] (S.L.); [email protected] (F.L.) 2 Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX 75080, USA; [email protected] 3 Chinalco Shenyang Non-Ferrous Metal Processing Co., Ltd., Shenyang 110108, China; [email protected] 4 Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; [email protected] * Correspondence: [email protected]; Tel.: +86-024-83687719 Received: 28 October 2020; Accepted: 25 November 2020; Published: 26 November 2020 Abstract: The electrochemical behavior and electrodeposition of Sn were investigated in choline chloride (ChCl)–urea deep eutectic solvents (DESs) containing SnCl2 by cyclic voltammetry (CV) and chronoamperometry techniques. The electrodeposition of Sn(II) was a quasi-reversible, single-step two-electron-transfer process. The average transfer coefficient and diffusion coefficient of 0.2 M Sn(II) in ChCl–urea at 323 K were 0.29 and 1.35 10 9 cm2 s 1. The nucleation overpotential decreased × − · − with the increase in temperature and SnCl2 concentration. The results of the chronoamperometry indicated that the Sn deposition on tungsten electrode occurred by three-dimensional instantaneous nucleation and diffusion controlled growth using the Scharifker–Hills model. Scanning electron microscopy (SEM) showed that the morphology of the deposits is uniform, as a dense and compact film prepared by potentiostatic electrolysis on Cu substrate.
    [Show full text]