DOCSLIB.ORG

Measurement of Counter Electrode Potential During Cyclic Voltammetry and Demonstration on Molten Salt Electrochemical Cells

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Measurement of Counter Electrode Potential During Cyclic Voltammetry and Demonstration on Molten Salt Electrochemical Cells International Research Journal of Pure & Applied Chemistry 15(1): 1-13, 2017; Article no.IRJPAC.37175 ISSN: 2231-3443, NLM ID: 101647669 Measurement of Counter Electrode Potential during Cyclic Voltammetry and Demonstration on Molten Salt Electrochemical Cells D. Sri Maha Vishnu1,2*, N. Sanil1 and K. S. Mohandas1 1Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, India. 2Materials Chemistry Group, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, United Kingdom. Authors’ contributions This work was carried out in collaboration between all authors. Author DSMV designed the study, performed the experimental work and wrote the first draft of the manuscript. Authors NS and KSM helped in analysis of the experimental data and suggested additional experiments to arrive at meaningful conclusions. All the authors managed the literature searches. All the authors read and approved the final manuscript. Article Information DOI: 10.9734/IRJPAC/2017/37175 Editor(s): (1) Wolfgang Linert, Institute of Applied Synthetic Chemistry Vienna University of Technology Getreidemarkt, Austria. Reviewers: (1) Fellah Mamoun, Abbes Laghrour University-Khenchela and Annaba University, Algeria. (2) C. N. Panagopoulos, National Technical University of Athens, Greece. Complete Peer review History: http://www.sciencedomain.org/review-history/21436 Received 3rd October 2017 th Original Research Article Accepted 14 October 2017 Published 17th October 2017 ABSTRACT In conventional cyclic voltammetry (CV) measurements, the potential of the working electrode (WE) is changed at a fixed scan rate w.r.t a reference electrode and the current response to the potential stimuli recorded. The current-potential data are in turn related to the redox behavior of the electro- active species in the electrolyte on the WE. The contribution of the counter electrode (CE) to the electrical signals has been suppressed by design to avoid its influence on the I-V characteristics of the WE. However, simultaneous measurement of the counter electrode potentials during CV measurements can provide useful qualitative information on the electrochemical process/es occurring at the CE and thus help in the comprehensive assessment of the overall electrochemical process/es under question. This has been demonstrated with tungsten and graphite WEs respectively against graphite and molybdenum CEs in CaCl2-x wt.% CaO melts (x = 0 and 1) at 1173 K. The technique has been applied to CV cell with Nb2O5 pellet as the WE against graphite _____________________________________________________________________________________________________ *Corresponding author: E-mail: [email protected], [email protected]; Vishnu et al.; IRJPAC, 15(1): 1-13, 2017 Article no.IRJPAC.37175 CE in CaCl2 melt and the results prove that preliminary information on the electro-deoxidation of the oxide electrode could be achieved by the novel measurements. Graphical abstract Keywords: Cyclic voltammetry; Counter electrode potential; Calcium chloride; Nb2O5; FFC Cambridge process; Electro-deoxidation. 1. INTRODUCTION electrochemical process/es occurring at the WE of the cell. This in other words means that the Cyclic voltammmetry (CV) is a potential- role of CE in a traditional CV experiment is controlled reversal electrochemical technique limited to its use as an electrode to complete the used extensively in the study of electrode cell circuit with WE, otherwise no information is reactions and mechanisms [1]. The CV cell sought to be obtained from the CE. comprises of three electrodes, viz. the working electrode (WE), the counter electrode (CE) and Though CV in its rigorous sense is generally the reference electrode (RE) and the electrolyte used as an analytical technique for study of solution in contact with the electrodes. In this fundamental electrode processes and technique, the working electrode is applied with a mechanism of redox systems, the technique can cyclic potential varying at a given scan rate w.r.t also be used in a simple manner to obtain both a reference electrode and the corresponding qualitative and quantitative information of currents are monitored. In a typical CV cell, the electrode processes occurring in an area of the CE is made very high compared to electrochemical cell. For example, the technique that of the WE so that the current density on the can be used to experimentally determine the latter becomes very high and that of the former electrochemical window of ionic melts like CaCl2 very low. This in turn ensures that the WE [2], LiCl [3] etc. and hence in the estimation of remains highly polarized and the CE negligibly standard free energy of formation of the salts polarized so that the electrical responses in the [2,3]. This information is necessary while carrying cell circuit can be attributed mainly to the out electrolysis experiments in the molten salts. 2 Vishnu et al.; IRJPAC, 15(1): 1-13, 2017 Article no.IRJPAC.37175 Further, the absence of any irregular current gaining insight into the electro-deoxidation of the wave/s between the discharge potentials of the oxide electrode and also in the operation of the cation and anion of the electrolyte melts gives a electro-deoxidation cells. All the demonstration clear indication that the melts are free of any experiments, reported in this study, were carried significant redox active impurities. Mohandas et out with electrode/electrolyte systems whose al. [4] employed the technique to obtain semi- reactions were well studied and reported before quantitative information on the anodic so that the potential-current data of the CV- intercalation and cathodic de-intercalation of CEPM measurements could be correlated to the chlorine occurring on graphite in NaAlCl4 melts at known electrode reactions of each system 425 K - 580 K and in turn used the results to studied. A rigorous study and analysis of the study the physical degradation of graphite electrochemical behavior of the WE w.r.t. scan anodes in the melt and its temperature rate is not warranted in this kind of dependence. The technique was also used to measurements and hence the measurements distinguish between the adsorption and were carried out at a single scan rate (20 mV/s) intercalation of chlorine occurring on anodically only. polarized graphite electrode in NaAlCl4 melts [5]. The CV technique has been used very effectively 1.1 The CEPM Measurement to obtain qualitative information on different electrode reactions of both the electrodes of While recording the cyclic voltammogram of a molten salt electro-deoxidation cells [2,6-8]. In WE, electrochemical reaction/s corresponding to most of these measurements CV technique was that occurring at the WE takes place at the CE. used only in a limited sense, i.e. to apply a cyclic The potential of the CE is left free and allowed to potential to the working electrode and to obtain float while running a conventional CV. In CV- the corresponding currents, which in turn could CEPM, the counter electrode potential w.r.t. be related to the reaction taking place at the reference of a CV cell is simultaneously working electrode. We have studied the electro- measured using a high-impedance voltmeter and deoxidation behavior of TiO2 [9-10] and Nb2O5 [3] the measured potentials are related to the electrodes in CaCl2 melt with graphite anode and electrochemical process/es occurring at the UO2 electrode in LiCl-Li2O and CaCl2-48mol.% electrode. The half cell reaction/s at the WE (CV) NaCl melts with both graphite [11,12] and when combined with the corresponding half cell platinum anodes [2,12]. The CV technique was reaction/s at the CE (CEPM) together defines the used extensively in these studies to determine overall electrochemical process/es taking the electrochemical window of the molten salts place in the cell and thus serves as a good and also to understand the electrochemical source of first-hand information on the net cell behavior of the oxide working electrode and reaction/s. graphite and/or platinum counter electrodes. During these measurements, it was observed 1.2 Application of CV-CEPM that practically useful information on the electro- Measurement on Molten Salt Electro- deoxidation cells can be obtained by measuring deoxidation Cell the potential of the counter electrodes, which otherwise is ignored. The counter electrode Direct electrochemical deoxidation of solid metal potential measurement (CEPM) presented in this oxides to metal in the ‘FFC Cambridge process’ article is thus a simple extension of the CV is an interesting area of development in technique to derive first hand information on electrometallurgy and significant R&D work has electrode processes occurring at the CE of a CV been reported in this area [13,14]. The cell. The technique has been demonstrated with electrolytic process is carried out by configuring tungsten and graphite WEs against graphite and the oxide electrode, generally prepared as a molybdenum CEs respectively in pre- pellet by powder compaction and sintering, as electrolysed CaCl2 and CaCl2-1wt.% CaO melts the cathode against graphite counter electrode in at 1173 K. The novel measurements carried out calcium chloride melt at ~ 1173 K. During the on a CV cell with Nb2O5 pellet as the WE against process, the oxygen present in the metal oxide is 2- graphite CE in CaCl2 melt demonstrated its ionized to O ions (oxygen ionization) and capability to provide qualitative information of the released to the electrolyte melt. The ions multiple electrode reactions occurring on both subsequently discharge as CO and/or CO2 gas cathode and anode of the molten salt electro- at the graphite anode even as the metal oxide deoxidation cell. Such information, gained rather electrode converts itself to the corresponding quickly from a single experiment, is helpful in metal. The electrode reactions can be written as 3 Vishnu et al.; IRJPAC, 15(1): 1-13, 2017 Article no.IRJPAC.37175 - 2- MO2 + 4e → M + 2O (at the oxide cathode) molten salt was pre-electrolysed at 2.8 V for 6 (1) hours to remove moisture and redox active impurities present in it and subsequently allowed O2- + C → CO + 2e- (at graphite anode) (2) to cool overnight.
Load more

Recommended publications
  • 07 Chapter2.Pdf
    22 METHODOLOGY 2.1 INTRODUCTION TO ELECTROCHEMICAL TECHNIQUES Electrochemical techniques of analysis involve the measurement of voltage or current. Such methods are concerned with the interplay between solution/electrode interfaces. The methods involve the changes of current, potential and charge as a function of chemical reactions. One or more of the four parameters i.e. potential, current, charge and time can be measured in these techniques and by plotting the graphs of these different parameters in various ways, one can get the desired information. Sensitivity, short analysis time, wide range of temperature, simplicity, use of many solvents are some of the advantages of these methods over the others which makes them useful in kinetic and thermodynamic studies1-3. In general, three electrodes viz., working electrode, the reference electrode, and the counter or auxiliary electrode are used for the measurement in electrochemical techniques. Depending on the combinations of parameters and types of electrodes there are various electrochemical techniques. These include potentiometry, polarography, voltammetry, cyclic voltammetry, chronopotentiometry, linear sweep techniques, amperometry, pulsed techniques etc. These techniques are mainly classified into static and dynamic methods. Static methods are those in which no current passes through the electrode-solution interface and the concentration of analyte species remains constant as in potentiometry. In dynamic methods, a current flows across the electrode-solution interface and the concentration of species changes such as in voltammetry and coulometry4. 2.2 VOLTAMMETRY The field of voltammetry was developed from polarography, which was invented by the Czechoslovakian Chemist Jaroslav Heyrovsky in the early 1920s5. Voltammetry is an electrochemical technique of analysis which includes the measurement of current as a function of applied potential under the conditions that promote polarization of working electrode6.
    [Show full text]
  • Convergent Paired Electrochemical Synthesis of New Aminonaphthol Derivatives
    www.nature.com/scientificreports OPEN New insights into the electrochemical behavior of acid orange 7: Convergent paired Received: 24 August 2016 Accepted: 29 December 2016 electrochemical synthesis of new Published: 06 February 2017 aminonaphthol derivatives Shima Momeni & Davood Nematollahi Electrochemical behavior of acid orange 7 has been exhaustively studied in aqueous solutions with different pH values, using cyclic voltammetry and constant current coulometry. This study has provided new insights into the mechanistic details, pH dependence and intermediate structure of both electrochemical oxidation and reduction of acid orange 7. Surprisingly, the results indicate that a same redox couple (1-iminonaphthalen-2(1H)-one/1-aminonaphthalen-2-ol) is formed from both oxidation and reduction of acid orange 7. Also, an additional purpose of this work is electrochemical synthesis of three new derivatives of 1-amino-4-(phenylsulfonyl)naphthalen-2-ol (3a–3c) under constant current electrolysis via electrochemical oxidation (and reduction) of acid orange 7 in the presence of arylsulfinic acids as nucleophiles. The results indicate that the electrogenerated 1-iminonaphthalen-2(1 H)-one participates in Michael addition reaction with arylsulfinic acids to form the 1-amino-3-(phenylsulfonyl) naphthalen-2-ol derivatives. The synthesis was carried out in an undivided cell equipped with carbon rods as an anode and cathode. 2-Naphthol orange (acid orange 7), C16H11N2NaO4S, is a mono-azo water-soluble dye that extensively used for dyeing paper, leather and textiles1,2. The structure of acid orange 7 involves a hydroxyl group in the ortho-position to the azo group. This resulted an azo-hydrazone tautomerism, and the formation of two tautomers, which each show an acid− base equilibrium3–12.
    [Show full text]
  • Chapter 3: Experimental
    Chapter 3: Experimental CHAPTER 3: EXPERIMENTAL 3.1 Basic concepts of the experimental techniques In this part of the chapter, a short overview of some phrases and theoretical aspects of the experimental techniques used in this work are given. Cyclic voltammetry (CV) is the most common technique to obtain preliminary information about an electrochemical process. It is sensitive to the mechanism of deposition and therefore provides informations on structural transitions, as well as interactions between the surface and the adlayer. Chronoamperometry is very powerful method for the quantitative analysis of a nucleation process. The scanning tunneling microscopy (STM) is based on the exponential dependence of the tunneling current, flowing from one electrode onto another one, depending on the distance between electrodes. Combination of the STM with an electrochemical cell allows in-situ study of metal electrochemical phase formation. XPS is also a very powerfull technique to investigate the chemical states of adsorbates. Theoretical background of these techniques will be given in the following pages. At an electrode surface, two fundamental electrochemical processes can be distinguished: 3.1.1 Capacitive process Capacitive processes are caused by the (dis-)charge of the electrode surface as a result of a potential variation, or by an adsorption process. Capacitive current, also called "non-faradaic" or "double-layer" current, does not involve any chemical reactions (charge transfer), it only causes accumulation (or removal) of electrical charges on the electrode and in the electrolyte solution near the electrode. There is always some capacitive current flowing when the potential of an electrode is changing. In contrast to faradaic current, capacitive current can also flow at constant 28 Chapter 3: Experimental potential if the capacitance of the electrode is changing for some reason, e.g., change of electrode area, adsorption or temperature.
    [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]
  • Cyclic Voltammetry
    Cyclic Voltammetry Denis Andrienko January 22, 2008 2 Literature: 1. Allen J. Bard, Larry R. Faulkner “Electrochemical Methods: Fundamentals and Applications” 2. http://www.cheng.cam.ac.uk/research/groups/electrochem/teaching.html Chapter 1 Cyclic Voltammetry 1.1 Background Cyclic voltammetry is the most widely used technique for acquiring qualitative information about elec- trochemical reactions. it offers a rapid location of redox potentials of the electroactive species. A few concepts has to be introduced before talking about this method. 1.1.1 Electronegativity Electronegativity is the affinity for electrons. The atoms of the various elements differ in their affinity for electrons. The term was first proposed by Linus Pauling in 1932 as a development of valence bond theory. The table for all elements can be looked up on Wikipedia: http://en.wikipedia.org/wiki/Electronegativity. Some facts to remember: • Fluorine (F) is the most electronegative element. χF = 3.98. • The electronegativity of oxygen (O) χO = 3.44 is exploited by life, via shuttling of electrons between carbon (C, χF = 2.55) and oxygen (O): Moving electrons against the gradient (O to C) - as occurs in photosynthesis - requires energy (and stores it). Moving electrons down the gradient (C to O) - as occurs in cellular respiration - releases energy. • The relative electronegativity of two interacting atoms plays a major part in determining what kind of chemical bond forms between them. Examples: • Sodium (χNa = 0.93) and Chlorine (χCl = 3.16) = Ionic Bond: There is a large difference in electronegativity, so the chlorine atom takes an electron from the sodium atom converting the atoms into ions (Na+) and (Cl−).
    [Show full text]
  • Supporting Information Redox-Active and Semi-Conducting Donor
    Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is © The Royal Society of Chemistry 2018 Supporting Information Redox-active and Semi-conducting Donor-Acceptor Conjugated Microporous Polymers as Metal-free ORR Catalysts Syamantak Roy,a Arkamita Bandyopadhyay,b Mrinmay Das,c Partha Pratim Ray,c Swapan K. Patib and Tapas Kumar Maji*a a Molecular Materials Laboratory, Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore-560064, India b New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore- 560064 c Department of Physics, Jadavpur University, Kolkata -700032 Table of Contents Physical Measurements ..................................................................................................................2 Computational Details ....................................................................................................................3 Electrochemical Measurements ......................................................................................................3 Experimental Section......................................................................................................................5 IR Spectra .......................................................................................................................................7 PXRD .............................................................................................................................................7
    [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]
  • Electroanalytical Methods: Guide to Experiments and Applications, 2Nd
    Electroanalytical Methods Fritz Scholz Editor Electroanalytical Methods Guide to Experiments and Applications Second, Revised and Extended Edition With contributions by A.M. Bond, R.G. Compton, D.A. Fiedler, G. Inzelt, H. Kahlert, Š. Komorsky-Lovric,´ H. Lohse, M. Lovric,´ F. Marken, A. Neudeck, U. Retter, F. Scholz, Z. Stojek 123 Editor Prof. Dr. Fritz Scholz University of Greifswald Inst. of Biochemistry Felix-Hausdorff-Str. 4 17487 Greifswald Germany [email protected] ISBN 978-3-642-02914-1 e-ISBN 978-3-642-02915-8 DOI 10.1007/978-3-642-02915-8 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2009935962 © Springer-Verlag Berlin Heidelberg 2010 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: WMXDesign GmbH, Heidelberg Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Electroanalytical Methods Fritz Scholz dedicates this book to the memory of his late parents Anneliese and Herbert Scholz Preface to the Second Edition The authors are pleased to present here the second edition of the book “Electroanalytical Methods.
    [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]
  • Experiment 3: Cyclic Voltammetry (Dated: July 7, 2010)
    Experiment 3: Cyclic Voltammetry (Dated: July 7, 2010) I. INTRODUCTION Redox reactions of quinone compounds have found application in many areas of chemistry and biology, such as photosynthesis [1], anthracycline cytostatic drugs [2], and wood and paper chemistry [3]. In this exercise cyclic voltammetry is used to study the redox processes and solvent hydrogen bonding effects in 2,3,5,6-tetramethyl-1,4- benzoquinone (duroquinone; see Fig. 1) [4–6]. The importance of hydrogen bonding in physico-chemical processes is enormous. For example, the liquid state of water and the helical structure of DNA are attributed to hydrogen bonding. FIG. 1: Stucture and reduction scheme of duroquinone. The structure shown for the anion radical is one of the two possible resonance structures, where the unpaired electron and the negative charge may exchange. Note that the neutral species is not aromatic. Voltammetry is a collection of electro-analytical techniques in which information about the analyte or a physical processe is derived from the measurement of current as a function of applied potential. It is widely used by chemists for non-analytical purposes including fundamental studies on redox processes, adsorption processes on surfaces, electron transfer mechanisms, and electrode kinetics. II. CYCLIC VOLTAMMETRY Voltammetric measurements are carried out using an electrochemical cell made up of three electrodes immersed in a solution containing the analyte and an excess of a nonreactive electrolyte called the supporting electrolyte. One of the three electrodes is the working electrode, which is typically made of platinum, gold, silver, glassy carbon, nickel, or palladium. The redox process occurs at this electrode.
    [Show full text]
  • A Brief Study of Cyclic Voltammetry and Electrochemical Analysis
    International Journal of ChemTech Research CODEN (USA): IJCRGG, ISSN: 0974-4290, ISSN(Online):2455-9555 Vol.11 No.09, pp 77-88, 2018 A Brief Study of Cyclic Voltammetry and Electrochemical Analysis *1Joshi P.S., 2Sutrave D.S. 1Walchand Institute of Technology, Solapur University, Solapur, Maharashtra, India 2D.B.F Dayanand College of Arts and Science, Solapur University, Solapur, Maharashtra-413006, India Abstract : Electrochemistry is defined as the branch of chemistry that examines the phenomena resulting from combined chemical and electrical effects. This paper covers some of the common voltammetry techniques which are currently in use. Cyclic voltammetry is a widely used technique in electrochemistry .The cyclic voltammetry is a powerful tool to study the electrochemical behavior of a system by systematic study of current-voltage measurements of a given electrochemical cell. Brief study of cyclic voltammetry and the analysis of an electrochemical cell from cyclic voltammogramis described. I. Introduction Owing to the good stability, high power density and moderate energy compared to the conventional capacitors and batteries, electrochemical capacitors (supercapacitors, also called ultracapacitors) are the attractive power sources. The application of electrochemical capacitors lies in the field where high power density is required with small or short currents such as during start-up of electric vehicles or in power back-up systems (UPS)1.Energy storage in supercapacitor is due to the pure electrostatic interaction between the charged capacitor plates and the ions from the electrolyte solution and the processes associated with the redox reactions of electrode material. Usually, in the electrical double layer capacitors the materials used as electrodes are activated carbons, metal oxides or conductive polymers.
    [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]