I am working on electrochemical studies on water oxidation catalysts. I am trying to do pH-dependent CV with electrolyte solution of sodium triflate and sodium hydroxide using GC electrolyte, platinum wire and Ag/AgCl reference electrode. However, I observed a peak at 1.3V for the electrolyte solution. Is this because sodium hydroxide is not analytical grade? (sodium triflate is pure) I have seen CVs with 0.1M NaOH with no peaks from 0.2 to 1.7V in the literature.
It is possibly due to an impurity. However if the impurity amount is very small it may get deposited. Alternately you may want to electrolyze the solution with larger size Pt or Glassy carbon electrodes to purify the solution and then try the CV. If it is only sodium hydroxide solution you can even use nickel electrodes to purify
Maybe the CVs in the literature were zoomed out so you didn't see it or were at different scan rates.
I recommend purchasing a different batch of the NaOH and Na Triflate and repeating it. If you stiil see it, it might not be an impurity.
Does it go away after the first scan or two? That could also be a sign of an impurity.
I agree. Buy the best sodium hydroxide pellets ( Analar or Analytical grade) and dissolve in Double distilled water. This should reduce impurity levels and if the extra peak is due to impurities you will not see it in this solution.
There is no peak for the first two scans. Then, the peak start to appear, which gets bigger and bigger as the scan continues. The first scan current is 75 microA, then it increases to 200microA in the second scan.
I suspect that you are generating some species from the anode ( counter electrode?) or the reference electrode is leaking something in to the solution in the first two cycles and gradually its concentration appears to be increasing. Check all the electrodes for impurities. Check wither some mercury or mercury sulfate is leaching out form the reference electrode.
Thank you Srinivasan, I have noticed bubbles in my GC electrode and the counter electrode. So I suspect, water is being oxidized. I use two compartment electrochemical cell to avoid the effect of any kind of leakage from the reference electrode.
Is your cell isolates the counter electrode ( GC) from the working electrode with a glass frit or a diaphragm. If there is an impurity generated at the GC,and is diffusing in to the working electrode vicinity you may see the peak appearing after sometime since you are not stirring the electrolyte. When you have the glass frit the impurity may still diffuse through the glass frit but will be slower. Check it out. You can substitute the GC with a Pt counter electrode and see whether the problem still persists.
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