yes I agree with Dr Umair Gulzar

Umair Gulzar ,

You can also Alireza Valipour , check this link for steps, if you are using same software

https://www.ecochemie.nl/download/NovaTechNotes/NOVA_technical_note_4_-_Calculating_the_current_density_xNOVA_1.10x.pdf

The max current is not [typically] the capacitive current. Capacitive current is the background current in the CV, while peak currents come from Faradaic reactions. If you apply a linear sweep across a capacitor you get a constant current, with a slight rise time due to resistance slowing things down (RC time constant). There is, however, a catch: you must be using either a surface mode for data acquisition or a linear (analog) scan generator. Most (modern, commercial) digital potentiostats do not capture all of the capacitive current unless they have one of those two features.

This paper may help you.

https://www.sciencedirect.com/science/article/abs/pii/S0378775309012142

Instead of (the current) i vs. Vr (scan rate) plot(s, in your question), you could plot (the calculated, nominal, Capacitance) C vs Vr. A CV (Cyclic Voltammetry) regime, having a pure Capacitive origin, converges to a limiting value CpureCap, a constant Capacitance value (CpureCap), in the C vs Vr diagram transformation.

So, you can consider[1] the ihigh (current) inside this Vr-regime, as a pure Capacitive current ( ihigh~ipureCap) for your target, e.g. calculate, only, the Capacitive (component of the) current density, from your curves' set of the exp. CV(s).

1. Name it, "i.Cap-condition"[2] for a Capacitive current.

2. In the case of a SC (SuperCapapacitor) you might find an additional (2nd converging) limiting value; the higher CpureCap value is due to the SC (condition).

Hi Valipour,

The capacitance of a supercapacitor ((F/g) versus scanrate (mV/s) can be calculated in experimental session of followed report, and then you can see a resulted plot in Fig. 5f.

Article A facile in-situ activation of protonated histidine-derived ...

Hope it can help.