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Chapter 25 Voltammetry 1 Voltammetric instrumentation

Chapter 25 Voltammetry 1 Voltammetric instrumentation. 1.1 Three electrodes voltammetry. Fig. 25-2 (p.718) A system for potentiostatic three-electrode linear-scan voltammetry. Fig. 25-8 (p.724) A three-electrode cell for hydrodynamic voltammetry. 1.2 Working electrodes.

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Chapter 25 Voltammetry 1 Voltammetric instrumentation

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  1. Chapter 25 Voltammetry1 Voltammetric instrumentation 1.1 Three electrodes voltammetry Fig. 25-2 (p.718) A system for potentiostatic three-electrode linear-scan voltammetry Fig. 25-8 (p.724) A three-electrode cell for hydrodynamic voltammetry.

  2. 1.2 Working electrodes At +E limit, oxidation of water to generate O2: 2H2O  4H+ + O2(g) + 4e- At -E limit, reduction of water to generate H2: 2H2O + 2e-  H2 + 2OH- Fig. 25-4 (p.720) Potential ranges for three types of electrodes in various electrolyte solutions

  3. 1.3 Excitation signals Fig. 25-1 (p.717) Potential excitation signals used in voltammetry

  4. 1.4 Voltammograms (voltammetric waves): graphs of current vs applied voltage Fig. 25-6 (p.722) Linear-sweep voltammogram for the reduction of a hypothetical species A to give a product P.

  5. 2 Hydrodynamic Voltammetry (Stirred Solution) 2.1 Concentration profiles at electrode surfaces (stirred solution) Fig. 25-12 (p.726) Flow patterns and regions of interest near the working electrode in hydrodynamic voltammetry Fig. 25-13 (p.727) Concentration profile at an electrode-solution interface during the electrolysis A + ne- P from a stirred solution of A.

  6. 2.2 Application of hydrodynamic voltammetry - Single voltammogram can quantitatively record many species provided enough separation between waves (01.~0.2 is required) - Problems with dissolved O2 – must purge solutions Further reduction of H2O2 water Reduction of O2 to hydrogen peroxide Fig. 25-16 (p.729) Voltammogram for the reduction of oxygen in an air-saturated 0.1M-KCl solution Fig. 25-14 (p.729) Voltammograms for two-components mixtures, with E1/2 differ by 0.1 V

  7. 3 Cyclic Voltammetry (unstirred solution) On a single electrode apply both anodic and cathodic sweep. 3.1 Fundamental studies System is reversible if E = 0.0592/n and ipc = ipa Note: Epc = E0 -1.1RT/nF 3.2 Quantitative analysis (not common)

  8. Switching potential Fig. 25-23 (p.737) Cyclic voltammetric excitation signal

  9. 3.1 Fundamental studies System is reversible if: E = 0.0592/n and and ipc = ipa Note: Epc = E0 -1.1RT/nF 3.2 Quantitative analysis (not common) Fig. 25-24 (p.738) a) Potential vs. time waveform and b) cyclic voltaqmmogram for a solution that is 0.6mM k3Fe(CN)6 and 1.0 M in KNO3

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