Cyclic Voltammetry (CV)

1. Preparation of Electrolyte Solution

1. Prepare an electrolyte stock solution (10 mL) composed of 0.1 M [Bu₄N][BF₄] in CH₃CN.
2. Place the electrolyte solution in the electrochemical vial, add a small stir bar, and place the cap onto the vial as shown in Figure 1.
3. Check to ensure that the nitrogen lead is in the electrolyte solution. Stir and degas the electrolyte solution with a gentle stream of dry N₂ gas (~10 min) to remove redox active molecular oxygen.
4. During step 1.3, carefully insert the working electrode (e.g. glassy carbon), counter (Pt), and reference electrodes (Ag/AgNO₃) into the Teflon cell top. Connect the cell stand leads to the appropriate electrode.

Figure 1. Setup of an electrochemical cell.

2. Obtaining a Background Scan

1. Define the experimental conditions for the solvent. For acetonitrile, the scan window is typically +2,000 mV – -2,000 mV.
2. Run and save voltammograms of the electrolyte solution at a range of scan rates (e.g. 20 mV/s, 100 mV/s, and/or 300 mV/s).
3. Check the resulting scan to ensure that there are no impurities in the electrolyte solution or remaining oxygen. A clean system will have no redox events. If the setup is contaminated, the electrodes and glassware will need to be cleaned and the electrolyte solution remade using clean components.

3. Preparation of Analyte Solution

1. Combine the analyte (~2-5 mM, final concentration) of interest with the electrolyte solution prepared above.
2. Check to ensure that the nitrogen lead is in the electrolyte solution. Stir and degas the analyte/electrolyte solution with a gentle stream of dry N₂ gas (~10 min) to remove redox active molecular oxygen.

4. Cyclic Voltammetry of Analyte

1. Perform multiple cyclic voltammogram experiments at scan rates from 20 mV – 1,000 mV (dependent upon the cell stand capabilities). Begin each scan using the calculated open circuit potential.
2. Methodically vary the scan direction [(+ to –) and (– to +)] and scan window to isolate redox events of interest. The voltammogram should always start from zero current (open circuit). Ferrocene (Fc) undergoes an oxidation reaction to ferrocenium (Fc⁺).
3. Many groups standardize data to the Fc/Fc⁺ redox couple. In this practice, ~2 mg of Fc are added to the analyte solution and step 4.2 is repeated for referencing purposes. In data analysis, all spectra are normalized to the Fc/Fc⁺ couple set to 0.00 V. A table of normalized reduction potentials is available².

5. Cleaning of Electrodes and the Electrochemical Cell

1. Carefully unclamp and remove each electrode from the electrochemical cell.
2. Rinse the reference electrode with acetonitrile and dry with a Kimwipe. Store in reference electrode storage solution.
3. GENTLY clean the working and counter electrode according to guidelines from manufacturers (e.g. BASi: http://www.basinc.com/mans/pguide.pdf) to remove the redox reaction products that accumulate during some experiments.