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Experiment

  • Page ID
    60712
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    Equipment

    • Obtain instructions on the use of a 3-electrode potentiostat from your laboratory instructor.
    • Electrochemical cell and electrodes
      • A 3 - 4 mm diameter (planar) glassy carbon or Pt working electrode
      • Pt auxiliary electrode
      • Ag/AgCl reference electrode
      • Small volume electrochemical cell
      • Polishing kit
    • Volumetric flasks with ground glass stoppers and pipettes

    Chemical Solutions

    1. 100 ml of 1.0 M KNO3
    2. 100 ml stock solution of 10 mM potassium ferricyanide [K3Fe(CN)6] in 0.1. M potassium nitrate [KNO3]
    3. An unknown concentration of potassium ferricyanide solution provided by instructor (optional).

    Procedure

    1. Polishing: Prepare the working glassy carbon electrode by first lightly polishing the electrode surface with 1 μm or smaller particles of alumina (wet) on a flat polishing plate. Wash the electrode carefully with pure water to remove any alumina. If a sonicator is available, fill a small beaker with pure water, place the electrode (tip down) and sonicate for 1 minute. Remove, rinse with pure water and touch the edges of the tip with Kimwipe or clean tissue paper but do not touch the electrode surface.
    2. Prepare 1, 2, 5 and 8 mM ferricyanide in 0.1 M KNO3 in 50 ml volumetric flasks.
    3. To run background scan, insert the electrodes (GC, reference Ag/AgCl and Pt auxiliary) and fill the cell with 0.1 M KNO3 until the ends of the electrodes are immersed. Add stirring bar and turn ON the magnetic stirrer to stir the solution so that there is homogeneity of concentration from the surface of the electrode to the bulk solution. After the stirrer is turned OFF, if any tiny gas bubbles should be adhering to the bottom of the electrodes, lightly tap the electrode to dislodge them. If a stirrer is not used, wait ~ 2 minutes before each scan to allow equilibration of the bulk concentration with that at the electrode surface.
    4. Run a CV scan from an initial potential (Ei) of + 600 mV to 0.0 mV and then back to + 600 mV at a scan rate of 100 mV/s. Repeat the scan after stirring the solution for 10-15 seconds and allowing the solution to quiet. The two voltammograms should match each other within 2-3 %. If not, re-polish the GC electrode and rerun.
    5. Run duplicate CVs on each ferricyanide solution (1, 2, 8 and 10 mM) at the scan rate of 100 mV/s.
    6. Run duplicate CVs on the 2 mM ferricyanide solution at scan rates of 20, 50, 200 and 500 mV/s.
    7. Label and save each CV with the “save function” if using a computerized potentiostat or print out a hardcopy of what you want to save.

    This page titled Experiment is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Contributor.

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