I prepare RGO by chemical method. I want to find the specific capacitance of my sample. I have taken CV by three electrode method for my sample. I used the following formula for calculation but I cant get the proper value. C= [Q/mxv ] x area of glassy carbon or C = {integrated area/ [m x v x V]} x Area of glassy carbon. It came like 0.23 F/g or 0.063 F/g. I find the integrated area using origin software and charge by CV equipment installed software itself. My active mass value is 0.0006 and potential window (V = -1.5 to 1.5) and scan rate (v = 50mV/s). I attached my graph below. Can anyone help me to get the proper specific capacitance value for my sample?
We normally take into account the mass of electrode to measure gravimeter capacitance of electrode. We use the following formula for this purpose in a two electrode cell. C = (2*Current) /(Scan Rate*Mass of electrode) - If you take Current in 'mA' measured from cyclic voltammogram , Scan Rate in 'Volts', Mass of electrode in 'mg' - you will end up having Capacitance in F/g. Yeah you can use excel or origin for such calculations
We normally take into account the mass of electrode to measure gravimeter capacitance of electrode. We use the following formula for this purpose in a two electrode cell. C = (2*Current) /(Scan Rate*Mass of electrode) - If you take Current in 'mA' measured from cyclic voltammogram , Scan Rate in 'Volts', Mass of electrode in 'mg' - you will end up having Capacitance in F/g. Yeah you can use excel or origin for such calculations
Use EIS for an accurate measure (I find a cole/cole to be useful).
You need the surface of RGO that you are investigating not that of the GC carbon electrode it would be better to operate as indicated above by D McMillan by EIS, you will obtain the capacitance of both the GC electrode and that of the deposited RGO, , if you know that of your GC under the same conditions you can deduce that of your RGO
The estimation of the capacitance from CV is based on a very simple principle.
The charging current i = C x dE/dt.
where C is the capacitance, and in CV experiments, dE/dt is the scan rate, v.
The unists are: C in Farad, i in Ampere, and v in Volt/second.
In practical analyses, the current from a CV chart was read using the difference between cathodic and anodic scans at a given potential. In this case, delta i = 2 x C x v. When the difference is potential-dependent, the Capacitance C is potential dependent. When the dependency is small, the average value can be used for the analysis.
For modified electrodes, the capacitance also includes the base electrode/electrolyte interfacial capacitance. You should subtract the current recorded using an "unmodified electrode".
give me the area of integral i will calculate for you , one more thing is if you're interested in specific capacity in F/g than area of electrode unimportant
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I normally use origin to integrate the area on the CV curve and use that to calculate the specific capacitance.You can also perform charge/discharge experiments which are more accurate for calculation of specific capacitance.
This may be a small deviation from the question but out of interest, I notice that you use a very low mass for your experiments there,is there any specific reason for this?It may be helpful to increase the mass loading to about 2mg and see the effect of increasing loading mass on the capacitance. .
Raja M,
Can we send our data for determination? Please send your email ID. My email ID is [email protected]
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