If the reference electrode has not been used for a while it is often a good idea to remake it, particularly if the chloride layer on the silver is no longer all dark brown (strip the AgCl from the Ag wire with ammonia and redeposit, replenish the KCl storage solution and also clean the frit by sonicating in DI water to prevent blockages) as this may affect the potential you are applying therefore the deposition process. Another point to consider is that Ag/AgCl as a reference electrode is best (and very stable) in an aqueous chloride solution so there are common ions, so depending on your system it may be perhaps not the reference electrode for the job.

Thanks Ignacio,

Please have a look at attached figures, one for PANI and the other for PEDOT. What are your thoughts about the I/t curve?

I think that  you should insist on the working electrode.

I took the value of set potential from literature because I am using the same protocol as reported elsewhere. 

You may check which reference electrode they are using? the KCl concentration n the reference electrode was 3M or saturated. sometimes there is a leakage of K+ from the reference electrode.

I suggest also to check your reference electrode. You may compare with a more stable SCE.

I agree with Andera; the first step before and after each experiment is to check your reference electrode to see that it's working properly. There is also a difference in 3M or saturated one. If you ave stored your saturated one in 3M KCL for long time, it is not anymore saturated.

Dear Muhammad,

Just check your reference electrode doing cyclic voltammetry of a known redox probe in your naked working electrode. If you see the expected CV profile for the redox probe, including the appeareance of peaks at the correct potentials vs Ag/AgCl/KCl 3M and absence of ohmic resistance effect in the voltammogram, the reference shouldnt be an issue. Next, if all is fine, please consider the comment of Chaker Tlili that some likage of K+ and Cl- from the frit of the electrode into the solution might take place and this is interfering at some point in the polymerization process. To check the likage, just carry out CV of a working electrode such as gold in 0.01 M HClO4, cycling into the anodic region for gold oxide formation. A typical profile for gold in 0.01 M HClO4 after succesive cycling and stationary conditions for a clean surface should be obtained. If not, and a clear peak (not typical for gold) is observed in the region for gold oxidation then you should suspect of Cl- presence in the solution that absorbs in the gold surface leading to AuCl4- species in this potential region. Then, if Cl- is present in the solution, K+ should be leaking as well.  

In case, all is OK and your reference electrode is fine, then you should start to think in the way you are carrying out your polymerization and the cleanleaness of the working electrode before you start the reactions on it.

I hope this comment can help you at some point. Good luck,

Cheers

If the reference electrode has not been used for a while it is often a good idea to remake it, particularly if the chloride layer on the silver is no longer all dark brown (strip the AgCl from the Ag wire with ammonia and redeposit, replenish the KCl storage solution and also clean the frit by sonicating in DI water to prevent blockages) as this may affect the potential you are applying therefore the deposition process. Another point to consider is that Ag/AgCl as a reference electrode is best (and very stable) in an aqueous chloride solution so there are common ions, so depending on your system it may be perhaps not the reference electrode for the job.

Thank you all for very interesting comments.

I am using Ag/AgCl 3M KCl reference electrode, same as reported in the literature. I am doing electropolymerization inside porous polycarbonate template. I make one side of the template conductive by coating it with colloidal graphite(I tried Au sputtering as well). The monomer solution should penetrate into the pores and polymerize at the contact of membrane and coated graphite. But it did not happen at all.

I performed CV of EDOT monomer but the I/E plot was strange (see attached). I noticed that the membrane completely melt during the cycles (0 - 1.5V) which is quite unusual I guess. 

I look forward to comments.

I think   if the current is measured , the reference electrode  is not problem ,because  it indicate the potential difference with working electrode.  Are you used direct current in the electrodeposition?.    The problem may be the applied potential, and the small conductivity of the polycarbonate membrane.It is necessary to make the sputtering  with Au on the  bottom.   Or    Why not  to use AC (altern current) by to electrodeposite    the nanowires inside pores of polycarbonate

Ag-AgCl electrode is a very stable reference electrode. If you have any doubt in its performance using after a long time, it is better to chek its performance with a known system. If it is not o.k. better to replace it with a new one or follow the technique as mentioned by Dr.

It is right that Ag/AgCl is a stable reference electrode if it is stored properly. Otherwise, the potential reading may be not accurate. Do a cyclic voltammetry of hexacyanoferrate with an inert working electrode (such as Pt wire) with your Ag/AgCl and check if you can get a nice voltammetric wave.

You can always register the potential of your "problem"electrode against another "trustable" one (if you have one). All you need a is a tester and inmerse both electrodes in the same solution, for example KCl os KNO3 0.1M (aprox). If you measure less than 5 mV, then it is OK. If not, you can use it anyway, but you need to correct the applied potential according to your reading.

You can also do a CV experiment, as recomended before. But you need to check the value of the half peak potential is placed, not merely the shape.

Thank you all,

In order to check proper working of reference electrode, I have performed CV of 10 mM potassium ferricynaide/ferrocyanide redox couple in 0.5M KNO3 using my Ag/AgCl reference electrode and Pt plate working and counter electrodes. The difference of cathodic and anodic peak potentials is about 170 mV. Does this mean that the reference electrode is no more good?