Can anyone suggest a reference electrode for electrodeposition in aqueous solution? Which one is better between a Saturated Calomel Electrode (SCE) and an Ag/AgCl reference electrode?What is the difference between the two?
Ag/AgCl and Hg/Hg2Cl2 (calomel) are essentially equivalent in most respects (other than the potential of course) and In particular the filling solution is normally the same (the KCl concentration can be varied in either case, but that is up to the user). Thus in most cases it makes no significant difference which is used. These days Ag/AgCl tends to be more commonly used because the mercury content of SCE presents transportation problems due to the way Hg causes rapid corrosion of Al alloys. Chloride contamination effects depend on the construction (primarily the porosity of the connection to the solution), not the technology, and they can anyway be controlled by the use of an additional salt bridge. I believe (though I can't give a reference) that Ag/AgCl has an element of photosensitivity, so will pick up flicker from some light sources, and in general it tends to be noisier than SCE, though this will be affected by details of the construction. Thus for electrochemical noise measurements, where we want to measure noise at very low levels, SCE is preferred.
One advantage of Ag/AgCl is that it is relatively easy to fabricate, so it can be used to make unusual configurations, and it can be cheaper than SCE. Overall however, in most cases I would not be too concerned about which technology to use; what is important if you want high quality results, is to calibrate your electrode against reliable standards, and to handle it carefully..
You might want to use other, chloride-free electrodes in situations where Cl- must be avoided (I would regard the issue of liquid junction potentials to be more important that solution contamination in this context, as the former cannot be solved by use of additional salt bridges), but you will generally find them harder to obtain.
Ag/AgCl is better for electrochemical characterization such cyclic voltammetry, electrodepotion, impedance analysis because it has 0.149 redox potential and can be used in any kind of electrolyte having any pH.If we go through literature most of the researchers used Ag/AgCl ref. electrode for electrochemical depotions.
In acidic environment I suggest using a Hg/HgSO4
eg .doi 10.1002/cphc.201000148
As aforementioned by friends; Ag/AgCl is better, but if Cl- make problem in solution or deposition, I suggest SCE. Some positive ions such as Fe3+ has very small Ksp with Cl-. So very trace amount leaching of Cl- from reference electrode, make deposition in solution or deposit on your working electrode.
Even though pencil is cheap but its not pure graphite it is doped with Pb, Sn to increase hardness of pencil. So these doped materials can be electrodeposited on working electrodes.
Most of the researchers used graphite as counter electrode rather than reference electrode.
I agree with Prof. Zate. Its better to use standard reference electrode. Ag/AgCl will be best in Aqueous Or You can try the Pt-wire also in both Aqueous and Non-aqueous medium.
I agree Dr.Zate. For the reference I usually Use Ag/Agcl wire or Ag/AgCl (x M KCl). Pt, Graphie and/or glassy carbon are used as counter electrodes. Thanks Zate.
In aqueous solutionnyou can use Ag/AgCl in Cl- electrolyte and Hg/HgSO4 in sulfate electrolyte.also you can use SCE in organic and aqueous solution, the difference of these electrodes is tne potential.
Ag/AgCl and Hg/Hg2Cl2 (calomel) are essentially equivalent in most respects (other than the potential of course) and In particular the filling solution is normally the same (the KCl concentration can be varied in either case, but that is up to the user). Thus in most cases it makes no significant difference which is used. These days Ag/AgCl tends to be more commonly used because the mercury content of SCE presents transportation problems due to the way Hg causes rapid corrosion of Al alloys. Chloride contamination effects depend on the construction (primarily the porosity of the connection to the solution), not the technology, and they can anyway be controlled by the use of an additional salt bridge. I believe (though I can't give a reference) that Ag/AgCl has an element of photosensitivity, so will pick up flicker from some light sources, and in general it tends to be noisier than SCE, though this will be affected by details of the construction. Thus for electrochemical noise measurements, where we want to measure noise at very low levels, SCE is preferred.
One advantage of Ag/AgCl is that it is relatively easy to fabricate, so it can be used to make unusual configurations, and it can be cheaper than SCE. Overall however, in most cases I would not be too concerned about which technology to use; what is important if you want high quality results, is to calibrate your electrode against reliable standards, and to handle it carefully..
You might want to use other, chloride-free electrodes in situations where Cl- must be avoided (I would regard the issue of liquid junction potentials to be more important that solution contamination in this context, as the former cannot be solved by use of additional salt bridges), but you will generally find them harder to obtain.
Thanks Dear Dr. Robert for useful explanation. I think that if Cl- has a kind of interfere in his work, he can fill inside the reference electrode with KNO3 or use a salt bridge connection filled with KNO3, saturated or 3 M. The mobility of Cl- and NO3- is same and all nitrate materials are soluble.
I do support the Dr. Robert Cottis answer. In my opinion there is not any preference for the election of Ag/AgCl KCl(sat)or SCE. They are basically the same and the election of the reference electrodes should be irrelevant for the electrodeposition process. Well, the values of the cell potential are slight different i.e. around 50mV. Anyway, the leakage of chloride ions from the reference electrodes (through the salt bridge) could be a problem. You can hinder this process using an additional chamber with a second salt bridge, as mentioned. I think that the Ag/AgCl Kcl is more popular because it is easier to handle, also you should consider that silver is healthier than mercury.
Kasra - you could use KNO3 in a salt bridge, but not as the filling solution in the electrode, since the KCl plays a part in fixing the potential of the electrode.
Both Ag/AgCl and SCE can be used for your electodeposition in aqueous electrolytes. The potential difference between these two is -0.045, so 1V vs Ag/AgCl is equivalent to 0.955 V vs SCE. A big advantage of Ag/AgCl is that it's mercury-free. Hope, this info helps.
Ag/AgCl or calomel can be used as the reference electrode for the electrodeposition from aqueous electrolytes. But for the electrodeposition from non aqueous electrolytes non aqueous reference electrodes or pseudo reference electrodes such as platinum can be used. The supporting electrolyte in non aqueous reference depends on the electrolyte from which the deposition is carrying out. For more details regarding the reference electrodes refer, Electrochemical Methods: Fundamentals and Applications, Allen J. Bard, Larry R. Faulkner or Electrochemistry: Principles, Methods, and Applications, by Christopher M. A. Brett , Ana Maria Oliveira Brett
KCl is preferred because the ionic mobities of K+ and Cl- are similar, so potential changes in the liquid are minimised. If you are just concerned with a solution in which to store the electrode (with a KCl filling solution), it would be best to use KCl, but NaCl probably won't have that big an effect (but then what is the advantage of using NaCl, other than a small cost saving?)..
That all really depends on the experiments that you conduct. If you just need some kind of reference electrode that keeps your electrodeposition stable, a simple ag-wire will do just fine. Isn't perfectly stable or reproducible, but it works.
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