I have to check CV characteristic of my pseudocapacitor electrode which was made using reduced graphene oxide and ZnO nano particles.
I am using Ag/AgCl as reference electrode, Pt foil as a counter electrode and 2M KOH as an electrolyte and voltage range from -0.22V to -1 V.
During the scan I am getting high current due to the formation of bubbles (most probably O2) on the surface of counter electrode.
I want to check the redox reaction happening at electrode in basic medium, how can I modify my experiment to measure this?
Hello Anvesh,
Do you want to know what reaction is occurring where? on the working electrode or on the counter electrode?.
In your WE you should see any kind of peak noticing a redox process or, in the case of the HER (hydrogen evolution reaction) a high decrease in the current density (a higher negative value).
If you want to observe the redox happening on your CE you should transform it in your WE.
Hi,
If you are using a 3-electrode measurement, the counter electrode reaction should no influence the reading (it could, however, limit your reading in case it is too small, or if it is isolating, but I don't think this is the case here).
Assuming your counter electrode is large enough and conductive, you won't see its influence in a 3-electrode configuration.
Therefore, if you are unable to see your electrode's redox peaks due to a masking high current it's possible that you have another parasitic reaction occuring at your working electrode.
in 2M KOH the pH is ~14. This means that the hydrogen evolution reaction potential if -0.83V vs. SHE. If your Ag/AgCl reference electrode potential is 0.2V then the HER potential is -1V vs. Ag/AgCl. In theory you should then not see a current resulting from the HER. However, if your Ag/AgCl potential is lower than 0.2V this could be the case.
First of all I would suggest using an Hg/HgO reference electrode, because Ag/AgCl is not designed for such an alkaline environment and may deviate from its stated potential. Check again with an Hg/HgO reference electrode, and try not to go below the HER potential.
hello Jordi,
I want to see it on working electrode. It is showing abnormally high current which is not common in CV of pseudocapacitor. During the experiment, I could see the bubbles forming at the counter electrode (Pt foil) which I think is due to the oxidation of water on its surface, which might be the possible reason for excess current.
Hi Anvesh,
I have experience doing supercapacitor as well. I think my comments will be more beneficial to you.
1. Approximately (I don't know the concentration of your filling), the Ag/AgCl potential is converted to 0.21V and -0.59 V (vs. RHE). It is obvious HER will occur in your Pt counter electrode and the working electrode when the electrode potential is swept toward -0.59V, respectively.
HER theoretically occurs at 0 RHE. But due to the intrinsic kinetics barrier, it often needs some overpotential to occur. - 590 mV is enough for HER to proceed! While OER occurs at 1.23V theoretically.
2. My suggestion for you is to do a CV survey scan in BOARDER range first before you fix the potential range!
3. You should be able to see a sharp decrease of current in negative potential regime and a sharp increase of current in positive potential regime; these are due to the HER and OER, respectively.
The redox reaction of your active material is between these two points. Note: Same species of active material may have different working potential range, as it is dependent on the morphologies. Hence you cannot follow the literatures blindly.
4. Redefine your potential range between HER and OER. Make sure the potential defined is well cut off, i.e., no HER and OER occur AT ALL!
Cheers,
Shu Hearn
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