The problem with a two-electrode setup is that you cannot control the potential drops at both electrode/electrolyte interfaces, but in fact, both influence the electrochemistry despite the fact that you are usually only interested in the electrochemistry of your working electrode, and the counter (more or less) is not of interest for you. Thus you should always use a well characterized counter electrode in a two-electrode compartment, so that you know about the potetnial dependent reactions at this electode, and with the knowledge of those processes, you may interprete the currents/voltages of your working electrode with this particular counter electrode.

In a three electrode compartment, you do not have these problems as the reference electrode measures the actual potential in fromnt of your working electrode, and the potentiostat/galvanostat regulates current/voltages so that the desired value is obtained. The reactions at the counter electrode do not play a role (unless, of course, the current density should not be too alrge, i.e. the area of this conducting electrode should be large enough to carry the current).

Hope this helps, Dirk

Two electrode and three electrode cell is depends on experiments. If really you want measure the current as well as potential then three electrode system will help. Otherwise two electrode system is ok. For ex., in Electrodeposition, two way is there one is under controlled potential deposition and under controlled current deposition for both we are considering either current or potential so this experiments is two electrode system.

The problem with a two-electrode setup is that you cannot control the potential drops at both electrode/electrolyte interfaces, but in fact, both influence the electrochemistry despite the fact that you are usually only interested in the electrochemistry of your working electrode, and the counter (more or less) is not of interest for you. Thus you should always use a well characterized counter electrode in a two-electrode compartment, so that you know about the potetnial dependent reactions at this electode, and with the knowledge of those processes, you may interprete the currents/voltages of your working electrode with this particular counter electrode.

In a three electrode compartment, you do not have these problems as the reference electrode measures the actual potential in fromnt of your working electrode, and the potentiostat/galvanostat regulates current/voltages so that the desired value is obtained. The reactions at the counter electrode do not play a role (unless, of course, the current density should not be too alrge, i.e. the area of this conducting electrode should be large enough to carry the current).

Hope this helps, Dirk

In a 2-electrode system, the results obtained from a working electrodes can be compared only when you use exactly the same counter electrode (both in terms of material and area). Even varying the electrochemical cell will change the values. In fact 2-electrode measurements are only for the whole cell (such as a Solar cell) rather than for individual electrodes.

3-electrode system on the other hand can be used to study individual electrodes and data will be reproducible.

In short, if you are studying individual electrodes, use 3-electrode system. If you want study your whole cell, use a 2-electrode system.

2-electrode setups are also useful for battery performance testing purposes. In those cases, you are not interested in all the details of the processes, but in the performance, such as cycle life time, degradation, charge/discharge speed etc. So here a 2-cell system can be sufficient in many cases! If you are however interested in the details, then you should also make use of 3-electrode system ... Regards, Dirk

Thanks to all of you for valuable suggestions, but i think i hadn't explain my question well! I totally agree with potential application of two electrode or three electrode cell configuration, but my question is if you have a two electrode system what parameters you should disclose in order to fully define that system?

I appreciate the explanations given by Dr. Dirk. If your purpose is to conduct electrolysis or to optimise electrolysis process in particular electrodeposition you can simply use 2 - electrode system. At a constant applied voltage you can carry out electrolysis. But if you want to characterise the electrolysis process or mechanism involved in it you have to follow 3- electrode system. Using this you can measure single electrode potential. By following CV you can study the mechanism. Such facility will not be available in 2- electrode system. Moreover electrolysis at constant potential or at constant current mode (potentiostat or galvanstat mode) can be done by 3-electrode system.

The solution is: use a counter electrode with large surface area (100 times higher then a working electrode).