I don´t think that using Ag/AgCl electrode for alkaline electrolytes is a good idea.

While having alkaline electrolyte in working electrode compartment, there was NaCl or KCl in reference electrode compartments. So, the potential of Ag/AgCl electrode should be stable in both cases. But I see two main problems here.

1. There is a membrane potential at the interface between two electrolytes, in the first case 0.1 M NaOH | sat. NaCl and in the second case 0.1 M KOH | 4M KCl. It can be calculated or measured and then taken into account. But I am not sure that it was done.

2. There will be leaking of electrolytes from one compartment to another. The rate of the leaking depends on the electrode and cell constructions, it may be very slow or rather fast. There will be certainly Cl- present in working compartment, and basic pH in RE compartment.

I don´t think that using Ag/AgCl electrode for alkaline electrolytes is a good idea.

While having alkaline electrolyte in working electrode compartment, there was NaCl or KCl in reference electrode compartments. So, the potential of Ag/AgCl electrode should be stable in both cases. But I see two main problems here.

1. There is a membrane potential at the interface between two electrolytes, in the first case 0.1 M NaOH | sat. NaCl and in the second case 0.1 M KOH | 4M KCl. It can be calculated or measured and then taken into account. But I am not sure that it was done.

2. There will be leaking of electrolytes from one compartment to another. The rate of the leaking depends on the electrode and cell constructions, it may be very slow or rather fast. There will be certainly Cl- present in working compartment, and basic pH in RE compartment.

I think the main problem is the diffusion of Cl-ions from the reference electrode into the compartment of the working electrode, and the possible influence of the electrochemical reaction studied. I fear that especially the adsorption / desorption of iodide / iodine-adatoms discussed in one of the papers is affected by the co-adsorption of chloride, as both species tend to undergo a specific adsorption. In the case of the ORR on graphene, the influence may not be as large as on gold.

Best regards, Dirk

I've been using Ag/AgCl as my reference electrode in 1M KOH recently and I've found that my Ag/AgCl is a bit faulty, keep getting overload signals during CV test.

I had to change to a new Ag/AgCl in order to continue, seems that the old Ag/AgCl is unrecoverable. I've noticed it started working strangely when I see a tiny air bubble in Ag/AgCl near the membrane barrier but the electrolyte level is still the same in the Ag/AgCl.

So do you think I should switch to Hg/HgO or SCE for future testings?

Dear John,

I would propose to switch to an alkaline reference electrode (like Hg/HgO/ NaOH etc) - I also made bad experiences with the Ag/AgCl in alkaline solutions, while the Hg/HgO/NaOH worked well also over extended time periods (long - time experiments). So I would definitely switch to another RE if available. By the way, with a pieve of Pt-wire, a small bubble of Hg and some few mg of HgO you can easily build up your own Hg/HgO-RE. The only thing you should take care of when making your own RE is that the HgO powder should soak the alkaline solution, so that you can achieve good contact. If there is remaining gas in the HgO, your RE-potential will not be definded properly!

Best regards, Dirk

Dear John, I'm using Hg/HgO for my alkaline battery testing. Its give me consistent results.

Ya, thanks to all of you I've been using Hg/HgO since!

Hello everyone, I also want know which type reference electrode will good for 30-35% KOH or TMAH etching solution. As I am developing a Electrochemical Etch Stop process. Does anyone has experience with Electrochemical Etch Stop Process?

Thanks

A.Q.Ahsan

Check The Leak-Free reference electrode series, with no glass of porous junction. They should work in your application. www.2in.com

Using standard Ag/AgCl RE is not good idea as discussed above. One of the main problem is etching away the "frit/membrane" which isolates the main body with the electrolyte. For highly alkaline solutions http://www.als-japan.com/1390.html#defaultTab13 is recommended.

Dear Shahid,

so we end up again with Hg/HgO ... there are quite many papers starting in the 1950ies and 60ies employing highly concentrated KOH and NaOH solutions in relation to alkaline batteries - in most of those works they have used Hg/HgO reference electrodes. Unless you have the liquid Hg drop in this electrode, they are stable, reliable, and if you do not have the budget to buy an electrode which is ready for use, you can easily fabricate an electrode of similar performance on your own, you simply need a piece of Pt wire (some mm), some g of clean Hg, some mg of HgO, and some ml of NaOH or KOH solution ... Good luck, Dirk

Hi everyone, to add up to these discussion, Ag/AgCl is widely used as reference electrode in HClO4 acid. Is it desirable to use that ?. Is there is any common ion in both HClO4 and KCl/NaCl junction ?

Hi. these answers are very helpful, thanks. I was recently using a Hg/HgO commercial electrode. Suddenly it has stopped working. It seems that the alkaline membrane is not working. Is it possible to reactivate the membrane? besides, what is the best reaction vessel for electrochemical measurements under strongly alkaline medium (I guess it should not be glass!). 

Sure, When you use the Ag/AgCl in alkaline medium,, please asure the salt bridge is with it,