We use 3 electrodes. Is there any sequence to connect WE, RE, CE for RDE? Also, the positions of those electrodes in the electrolyte solution? I usually place left side is CE and right side RE and then between them WE were positioned at a little upper level.
I think your placements are OK. In cases of a bad conducting electrolyte you must be careful not to place the reference electrode between the WE and the CE because there might be an Ohmic drop effect and the RE measured the wrong potential. Many researcher also use a Luggin-caplillary closer to the WE surface but out of the main current pass flowing between the WE and CE.
Karl is completely right. Special care needs to be take if you use a pseudoreference electrode, such as silver wire. The chemical environment (chemical potential) of such electrode must not change during the potential scan, otherwise the potential fluctuates. It is advised to protect the pRE wire electrode by a glass mantle and position the tip close to the W electrode surface as far as possible from the counter electrode.
I have a general doubt here @ Karl Cammann . It is known that the current pass through WE and CE, whereas a high Impedance is kept between the WE and RE to avoid current passage. In such case, IR drop is nearly zero or negligible between WE and RE. When we do EIS of such system solution resistance measured is between WE and CE ? if the above statement is right, why we need to keep WE and RE close together to reduce the solution resistance ?. Is it only for improving the accuracy of potentials. In same system if we keep WE and CE close together can we improve the ESR of the system ?
In addition to the above, always connect the WE or CE last. If your potentiostat powers up the cell before you've completed connecting it (i.e. if the WE is not disconnected internally prior to the experiment starting), then you could put the maximum voltage between the WE and CE as the potentiostat tries to correct an uncorrectable error by passing current through the CE. This can have disastrous consequences for the WE if you oxidise the hell out of it. Similarly, always disconnect the WE first. Also, in some experiments, it's worth thinking about what the CE reaction is- it is usually water hydrolysis which will lead to local pH changes. You can minimise the impact of this by putting the CE behind a fritted disc and locating it well clear of the WE.
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