It would help a lot to see the CV. By inference though, I think you are confusing glassy carbon or pyrolytic carbon with GAC (granular activated carbon). In general GAC is made through steam activation. One would imagine that this process is very clean, and it kind of is, but there is little molecular level control over the residual active sites left on the carbon surface. Those sites can indeed be redox active....at least that would be my interpretation. If you are the inquiring type, try running a TGA or a DSC on your 'electrode'.

Thank you Scott Gordon-Wylie for your answer. Please find the Origin file of CV of AC for your reference. I have used same Activated carbon before for another experiment and it shows very good edlc nature. I am attaching this graph also.

It's a good start. Solvent blank CV? e.g. with an uncoated electrode.

Looks like weak irreversible reduction. That might be consistent with a chemical reaction followed by a diffusible species leaving the electrode surface. Try running the SAME CV say for 20-40 repetitions or so, see if it doesn't settle down to more of what you want. Is the solution stirred or stationary? That's something else to play around with a little...stirring...not too fast. Should give some insight into the diffusional component (poor man's ring/disc). Just checking, but what's the electrolyte?

Just some things to play with.

Scott Gordon-Wylie I will run CV of uncoated film and will share result with you. 2 M KOH was used as electrolyte in my experiments.

The rectangular shape of the CV (cyclic voltammetry) curve is typically observed for electrically double-layer capacitors (EDLCs) or supercapacitors, where the charge storage mechanism is purely electrostatic in nature. However, when activated carbon is deposited on a conductive substrate like nickel foam and immersed in an electrolyte like KOH, additional redox reactions can occur.

The presence of redox peaks in the CV curve suggests that in addition to the electrostatic double-layer capacitance, the activated carbon on nickel foam also exhibits pseudocapacitance behavior. This combination of electrostatic and faradaic charge storage mechanisms contributes to the overall capacitance and energy storage capabilities of the activated carbon-based electrode in KOH electrolyte.

Davoud Mousavi Yes I understood that point. I run a CV of bare Ni Foam and it seems that redox peaks are from Ni foam. Here maybe pseudocapacitance contribution is more than edlc. I am attaching image of CVs of AC, RGO, and Bare Ni foam. But I want EDLC nature of AC/RGO for assyemetric supercapacitor device on same Ni foam substrate. What can I do for that? (I washed Ni foam according to reported procedure i.e. with Acetone, ethanol, HCl, water).

Scott Gordon-Wylie I ran a CV of bare Ni foam (50 cycles), and it seems that redox peaks are from Ni foam. Here, maybe the pseudocapacitance contribution is more than edlc. I am attaching image of CVs for AC, RGO, and Bare Ni foam. But I want the EDLC nature of AC/RGO for an assyemetric supercapacitor device on the same Ni foam substrate. What can I do for that?

OK, things are becoming clearer now. The Ni foam control helps a lot. Reference electrode? i.e. where is this zero of potential located relative to a standard potential (like hydrogen or calomel or the like)? And relative scan rate...what is the scan rate relative to the process speed? If it is capacitive charging, then the scan rate should start to tell a story, high scan rates versus low scan rates...that's because the double layer is fast(er), but farther out is slow(er), that's why I suggested stirring which admittedly may be ineffective if the pore size is small. I think you are on your way to a better description. Davoud's comments also add considerable insight regarding the physical mechanisms. It really seems like you are trying to disentangle several different mechanisms...if so changing the scan rate should help..at least somewhat....e.g. 1 mV/sec out to say 10 V/sec (if you can get that fast) ...make some well chosen values in that range...things should become even clearer then...there's also some equations for electrochemical electron transfer rates, probably some other equations for capacitive charge rates. Sadly you are going to wind up with one CV curve and something like 10 parameters, conductivity, diffusion rate, electron transfer rate, concentration, ion activity, electrolyte contribution, scan speed...ta da...scan speed.....and don't forget the Fermi Levels which in more local terms would be related to the E0 values. Still, if you have a decent model, you can reduce that down a bit.

Perhaps a silly question Shamal, but what gas are you under (air, argon, nitrogen)?

Scott Gordon-Wylie was stirred a solution under air instead of an inert gas.

Hi Shamal,

Argon is da bomb diggety, well worth the extra $...that's because it's heavier than air, so just a very slow trickle of argon will keep ALL the air out.....2 needles and a septum, that's all you need, even parafilm with a tube in and a tube out and some tape will take you a long way. If you want to go old school, a rubber stopper, a cork borer, and a glass tube (be careful putting the glass tube in, use some mineral oil or vegetable oil to reduce the friction), then a tube & a T, just blow the argon by, very slowly, just make sure that you exit through a water trap, so there is a positive pressure of argon...I think you may be amazed at what a difference it can make, but be patient, 10 minutes of argon, minimum.

Scott Gordon-Wylie Ok, thanks a lot for your input.

I hope it's helpful. The best overall advice is have fun with it.