I am working on Nickel oxide materials for supercapacitor and I am using platinum wire and Ag/AgCl as my counter and reference electrodes respectively with 1M KOH as my electrolyte. initially i was able to do my CV measurement without any problem but now, the problem i am facing is when i start the CV measurement, there is a huge reaction with severe evolution of gas at the counter electrode which turns the KOH electrolyte black and dissolution of my material. The potential range im working in is 0 to 0.5V and before the CV measurement i measure the OCP and it is around -0.1 V. Please can anyone help me figure out why this problem is occurring?
i have attached some pictures which could be of help.
Dear Rania Nuamah
The potential range for CV that mention 0 to 0.5 V with respect to RHE or Ag/AgCl??
If it is vs Ag/AgCl, then i think you going to very high positive potential region (oxygen evolution reaction at working electrode and same time hydrogen evolution at counter electrode) as your electrolyte is 1 M KOH. At high positive potential evolve oxygen may peel of your materials from the electrode.
Best Regards,
Bapi
If the working electrode can't be polarised at 0.5 V vs. Ag/AgCl, then the counter electrode will be at a very negative potential.
Use a mV-meter to measure, during a CV cycle, the voltage between WE and CE, WE and REF, CE and REF. You will better understand what is happening.
If available, use a common potentiostat.
As my point of view you just fix the potential window 0.15 to 0.45V for nickel based compound. Usually the hydrogen is evolved during the anodic reaction in CV at the counter electrode (Pt). No worries, you fix the potential 0.15 to 0.45V at a scan rate of 10 mV/s for 1M of KOH solution.
The peal of the active materials is due to the improper binding, apt substrate, and proper drying ect.
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