Redox electrode
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A redox electrode is an electrode made from electron-conductive material and characterized by high chemical stability in the solution under test. It is used for measuring the redox potential of a specific redox system in solution, and for electrochemical studies (investigation of electrochemical kinetics of interfacial processes).
The correlation of an electrode potential and redox system composition can be described by the Nernst equation:
- Ox + ne- = Red
- <math>E=E^0 + {RT \over nF}*\ln \left ({a_{\mathrm{ox}} \over a_\mathrm{red}}\right )</math>,
where
- E0 - standard potential of a specific redox system,
- R - gas constant,
- T - temperature in kelvins,
- n - number of electrons taking part in a specific redox reaction,
- F - Faraday constant
- aox, ared - activity of oxidising and reducing participants in redox reaction.
There are two general classes of redox electrodes:
- metals (the most common are platinum and gold, but for special purposes other materials such as titanium or iridium can be used)
- semiconductors (the most common are graphite, diamond, and SnO2)
[edit] Illustration
Image:Redox electrode.jpg A gold disk redox electrode with a Teflon shroud insulating the disk.
