After each CV, the surface properties of your electrode may be different. These depend on the potential window you use.

Pay attention, your Ag/AgCl/Cl- reference electrode is not compatible with KOH solution (the frit may become blocked by Ag2O).

Thanks Cornel, I will change the electrolyte and voltage window and observe the outcome

Do you refresh the electrode and solution before each experiment? If not, the properties differ.

hi volodymyr,I never refresh the electrode,I repeat the experiment without changing anything,I will try your suggestion.

Dear Keith Sirengo,

Do you dropcast the catalyst ink... In that case some of your catalyst particles might get detached during the process leaving lesser number available for next time.. If you are using metal rod itself, some impurities might deposit at the surface of your electrode that could decrease the effective catalytic surface area for next run.

Dear Adhidesh Kumawat,

I didn't drop cast,I should try and see the outcome because I did more than 30 runs and the capacitance was constantly dropping

Dear Keith Sirengo,

could you show, please, some CV-graphs ?

Hi Keith,

I use to work with three-electrode cells but is common that, in many cases, the first scan (even the first two or three) CVs present a higher capacitive current. If we suppose there is no faradaic current, then the current depend on adsorption/desorption processes... and the state of the surface at the moment. I suppose that an equilibrium will be achieved at the e.g., third scan and I consider this is the one you have to consider.

Best

Dear Teresa,

Thanks for your kind respond but for my case i did more than 30 cycles and there was no equilibrium, I mean there was a constant drop!

Dear Keith,

The capacitive current can change when the potential (same scan always), electrode area, or solution composition changes. So, one of this three is changing. Why don't you use a third electrode as counter electrode in order to make the current flow between the counter and the working and maintain the reference with a stable potential?

Best regards

Dear Teresa/members,

Thanks for your answers,they really helped but I have got a cyclic voltammogram of the shape attached but I have a big doubt about the capacitance calculated from it,it is extremely high especially when the potential window increases.please consider the graph and let me read your comments

Dear Keith,

I am seeing the CV. Which is the process at ca. 0.4V??? Probably the surface is changing due to a faradaic process. You only have two electrodes and in my opinion you can repeat the experience with three electrodes to be sure you are applying always the same potential.

Best regards,

Teresa

Dear Teresa,

Am using three electrode system(platinum as counter,Ag/Agcl as reference and transition metal oxide composites as working electrode) with 6M KOH electrolyte

Dear Keith Sirengo,

some EIS measurement(s) will help (you) in a better understanding and why the capacitance is, constantly, dropping.