Links: Electrochemist's Guide, AfterMath User's Guide, AfterMath Main Support Page

Related Topics: post-experiment idle conditions, cell switching

During the time period between experiments, it is usually important to assure that conditions of the electrochemical cell do not allow any unwanted electrochemical processes to occur. A passive approach is to merely disconnect the cell from the instrument (either manually or automatically) and prevent any stray currents in the cell. A more active approach is to keep the cell connected to the instrument and carefully apply the appropriate signal levels to the electrode(s) to prevent any redox processes.

The AfterMath software allows you to control and monitor the condition of the electrochemical cell at any time when the instrument is idle. This control is provided by clicking on the instrument in the Instrument List and viewing the Instrument Status (see below). One of the tabs on the Instrument Status panel is the “Idle” tab. This tab has cell and electrode controls (top half) and also indicators showing cell status (bottom half).

In the example above, the first working electrode is set to a passive mode of operation (open circuit potential). In the status area (bottom half), you can see that the OCP level is -783.6 millivolts and the current has a magnitude of about 3 microamperes. In addition to the passive OCP mode of operation, you may choose three other modes of operation for an electrode: potentiostatic, galvanostatic, and zero-resistance ammeter (ZRA). When a working electrode idles in one of the two active states (potentiostatic or galvanostatic), then you may choose the signal level that is to be actively applied to the electrode. (see below).

In the example above, the first working electrode is idling in potentiostatic mode, and there is no control of any second working electrode (because the Pine WaveNow potentiostat does not support a second working electrode). The setpoint for the first working electrode potential is 40.0 millivolts. The actual potential of the first working electrode is monitored in real time in the status area (bottom half) on the Idle tab. You can see that in this example the “live potential” at the first working electrode is actually 39.8 millivolts and the “live current” is 42.0 milliamperes.

NOTE: The availability of the four modes of operation (potentiostatic, galvanostatic, OCP, and ZRA) depends upon the particular instrument model that you are using. Not all instruments support all four modes of operation on all electrodes.

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