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The Physical Electrochemistry package is meant for researchers who are performing studies in the area of electrochemistry. Included in the package are techniques for performing linear sweep and cyclic voltammetry experiments, as well as chronopotentiometry, chronoamperometry, chronocoulometry, and controlled-potential coulometry. Gamry's Resonator™ software also performs these techniques while simultaneously acquiring data from an eQCM 15M™.
In the Physical Electrochemistry's standard techniques, we follow the corrosion convention for current:
•Positive currents are anodic, resulting in an oxidation at the metal specimen under test.
This convention is the same as the current convention used in other Gamry software packages such as DC Corrosion and Electrochemical Impedance Spectroscopy.
Within the Gamry Echem Analyst 2™ software, the convention used to display current data can be changed using the Tools > Options > Units > Research Current Convention setting. Currents are displayed using the convention set here, independent of the convention used to record the data. This option applies to experiments included in the Physical Electrochemistry and Pulse Voltammetry.
Potentials can also be a source of confusion. Throughout Gamry's software, the equilibrium potential assumed by the metal in the absence of electrical connections to the metal is called the open-circuit potential, Eoc. We have reserved the term corrosion potential, Ecorr, for the potential at which no current flows, as determined by a numerical fit of current-versus-potential data. In an ideal case, the values for Eoc and Ecorr are identical. One reason the two voltages may differ in real systems is changes in the electrode surface during the scan. In Physical Electrochemistry, all potentials are specified or reported as the potential of the working electrode with respect to either the reference electrode or the open-circuit potential. The former is always labeled as "vs Eref" and the latter is labeled as "vs Eoc".
The equations used to convert from one form of potential to the other are:
Regardless of whether potentials are versus Eref or versus Eoc, one sign convention is used. The more positive a potential, the more anodic it is. More anodic potentials tend to accelerate oxidation.
The following references are useful for learning more about the techniques that are available in the Physical Electrochemistry:
1.Allen J. Bard and Larry R. Faulkner, Electrochemical Methods: Fundamental and Applications, John Wiley & Sons, New York (2000). ISBN 0-471-04372-9.
2.Kissinger and Heineman, Laboratory Techniques in Electroanalytical Chemistry, 2nd ed., CRC Press, 1996.
3.R. S. Nicholson and I. Shain, Anal. Chem., 36(1964), 706, and Anal. Chem., 37(1965), 178.
4.R. S. Nicholson, Anal. Chem., 37(1965), 1351.