Cyclic Voltammetry CurrentPotentialTime Space Time Reversible System A

Cyclic Voltammetry

Current-Potential-Time Space Time Reversible System

A New Waveform Potential waveform: E Ei 0

Diffusion Condition For the reversible case have the standard Semi-infinite diffusion conditions plus:

Solution 1948 Sevick, “Oscillographic Polarography with Periodic Triangular Voltage”, Collection of Czech. Chem. Comm. , 13, 349 (1948). Randles, “A Cathode Ray Polarograph”, Faraday Society, 44, 327 (1948).

Problem There is no analytical solution to Fick’s second law when the boundary is time dependent. Sevick and Randles solutions was to approximate the integral with a series. While this works for the reversible case, it is not very pragmatic for more complex mechanisms. New Solution: Wait for a high speed computer (IBM main frame -1964 University of Wisconsin at Madison) Nicholson and Shain, “Theory of Stationary Electrode Polarography”, Analytical Chemistry, 36, 706 (1964)

Reversible CV Continued

Don’t Miss this Table Myth: A reversible wave will have a 60 m. V peak to peak separation.

N&S Diagnostics

Two KEY Points 1. Should use all three diagnostics 2. MUST go over three orders in magnitude in scan rate to reliably use a diagnostic! Implication: A single CV scan doesn’t tell you much, don’t over interpret it!

The Baseline Issue Three solutions • Guess • Record i-t over i-V • Nicholson: Nicholson, Anal. Chem. 38, 1406 (1966)

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An EC Mechanism Cl. Re(CO)3 phen in acetonitrile (CH 3 CN) + tetrabutylammonium perchlorate Luong, Nadjo and Wrighton, JACS, 100, 5790 (1978)

Charge Transfer Communication