I suggest you export your data as ASCII format and than work with the file in a software for mathematical processing such Origin, MathLab etc. Which program is CHI? Can you give more details? Good luck!

Alternatively, you may take peak current divide it by scan rate and active mass, you will get specific capacitance. In my opinion, specific capacitance obtained from Charge-discharge profile is more authentic.

thanks alot  for your kind reply. I used the Origin parogram , and I draw plot and got the area. in fig(1) I draw two segments of CV as separate curves  and used multi curve. in fig(2) I draw it by symbol /scatter .which one is correct? i really appreciate your help.

best regards.

Capacitance = charge/ voltage

you know sweep rate ( voltage/ second)

current is in amperes

capacitance under the peak  =total charge under a peak / sweep rate

use this concept to calculate the capaciatnce

for super capacitors  you see my appers

sorry my papers

it is maximum current/ sweep rate = capacitance and not charge

Prof. Muralidharan,

The general equation, capacitance = charge/voltage, is only correct if the material or electrode or device behaves like a capacitor, for example, the cyclic voltammogram (CV) is rectangular in shape.

Your other equation (copied below) for calculating capacitance is incorrect.

     capacitance under the peak =total charge under a peak / sweep rate

(1) A peak shaped CV should not be used for calculation of the capacitance of the material or electrode.  

(2) Even if it is for calculation of the differential capacitance, your equation is still incorrect. It should be 

differential capacitance = current / sweep rate

This equation can be used for calculation of the electrode capacitance if the CV is rectangular. 

who said? for pseudo capacitance with CTR what you do?

rectangular case is for super capacitors only as there is no CTR

dear Prof George

i recalled my work  in 1980's

i did dimerization of aldehydes -Cv

the broad anodic peak appeard around 0.1 to 0.3V

the sweep rate is 10mV/ sec

the charge under the peak was calculated manually and later using planimeter

the number of small squares is the charge=Q

Q=  current multiplied by time

C= Q/V

this is intergrated capacitance

we use differential capacitance for double layer with out CTR

now people use ethanol oxidation - a case of pseudo capacitance with CTR

since 1973 i use the term  triangular voltammetry  not the term CV - please see my papers in J Appl Electrochem -- 1983-1984-1985

CV implies the input signal crosses zero - sinusoidal perturbation crossing zero axis we call AC

however people use the term

coming back to the subject of capacitance  i needed  the charge under the peaks to calculate the passive film thickness - my papers inJ Appl Electro Chem 1980

on wards-

 i  used Q values for porous iron electrodes - see my papers  with M.Jayalakshmi - papers appeared in J Power sources 1990's

Double layer capacitors and pseudo-capacitors are both capacitors, and their performances must follow the equations for capacitors, most importantly the one for calculation of energy:

Energy = (capacitance*voltage2)/2

This equation can be derived from integration of a linear (or triangular) potential-time plot recorded during constant current discharging (and charging). This requirement is equivalent for a rectangular cyclic voltammogram.  

If you use the "charge/voltage" ratio measured from a peak shaped CV as the capacitance, and bring it into the above equation for energy calculation, you will likely overestimate the energy for discharging, and underestimate it for charging, if the charge transfer reaction is not ideally reversible.  

Many charge transfer reactions can result in rectangular CVs in a limited potential range, giving rise to the concept of pseudo-capacitance. 

agreed  why you want to compare both - CV and charge/ discharge studies are done in different time domanin

For a reversible gas  adsorption/ desorption you will get a rectangular diagram -if it is reversible

Dear Prof George

now the time has come to define pure capacitance and pseudo capacitance

ideal capacitance is not leaky  -pseudo capacitance is leaky

from  your equivalent circuit    and  CPE   values  we can say  it is pure or  pseudo capacitance

Then all capacitances are pseudo

Dear Prof. Muralidharan,

In the context of supercapacitors, whether leaky or ideal, pseudo-capacitance results from charge transfer reactions in the material attached to the electrode with the charge flow rate (current) being unaffected by a linear potential variation against time.  My observation is that pseudo-capacitance is often shown by redox active semiconductor materials (conducting polymers and transition metal oxides) in which the valance electrons are delocalised in the conduction band, which effectively makes the energy change infinitely small for each electron transferred to or from the conduction band.

In your term, I can say capacitors are all non-ideal, but not necessarily pseudo according to the explanation above.   

dear dr

Semiconductor / electrolyte interface is different. Semiconductor stores charge

their electro chemistry is different.No interface has ideal capacitance and we use the term pseudo to distinguish between ordinary capacitance and the interfaces those behave like capacitance.

Dear Professors V.S. Muralidharan and Prof. George

Wether we will compare the capacitance values from CV and GCD studies. Please give the explanation for both comparing or not.

We do both in most of our research and find the results (capacitance) are often comparable, as expected (although I do not remember any case in which the two measurements produced very different capacitance values). However, apart from capacitance values, CVs and GCDs can provide different but complementary information. For example, CVs are helpful in identification of the reversibility of an electrode process in a particular potential window, whilst GCD allows the derivation of the energy efficiency of the charging/discharging processes under constant current.

Thanks for your imformation Prof. George

For example in CV the specific capacitance value is 106 F/g for 5 mV/s and in GCD it is 438 F/g for 2 mA/cm2 this kind of result is correct. can you give some suggestion of this professor.

Hi Manikandan,

I think this may be helpful for you. There's a paper by M. D. Stoller and R. S. Ruoff; 2010 ( DOI: 10.1039/c0ee00074d ) that discusses the various ways of calculating specific capacitance. They specifically compare Csp from CVs and GCDs and try to explain the difference. It might be useful.

Thank you Akash Ratnayaka

Dear Manikandan, I need to see your CVs and GCDs before offering my comment.

Dear Prof. 5a is the CV and 5c is the GCD file

Thanks for sharing the CVs and GCDs. Obviously, your GCD at 2 mA/cm^2 has a much longer time for charging than that for discharging. In other words, the GCD plot at 2 mA/cm^2 shows a great irreversibility, and hence is not suitable for capacitance calculation. If you still wish to have an approximate comparison, you should use the discharging branch of the GCD for calculation (which is still an overestimate because the plot is inward curved from a straight line.)

Thank you very much for your suggestion Prof. George

After looking at the CV scan, i think electrode resistance is more dominant, as indicated by the inclined charge/discharge curves. Also I think you should consider the IR correction to extract the current response from these CV curves. At the lowest current density, the increase in diffusion layer thickness can also limit the capacitive response due to the occurrence of faradaic but non-capacitive reactions as described by Dr. Chen.

Dear Nazanin Hamnabard

you can calculate of capacitance of electrode CV by this formila

C=I/scanrate*mass

Dear Kashif Mairaj Deen

you can calculate of capacitance of electrode CV by this formila

C=I/scanrate*mass

Anyone please give me the suggestion of the calculation.How to calculate double layer capacitance from cyclic voltammetry. But i did calculate Cdl in faradaic region. It is right or wrong. Here i attach image of cyclic voltametry different scan rate and Correspondig Cdl value. Please correct my doubt.

Thank you for your suggestion sir.