I am working on Thin Film materials. I want to calculate ECSA (cm2) , by double layer capacitance using CV mode. First i need to identify non-faradaic region (somewhere in between the hydrogen and oxygen region), will run CV at various scan (from more positive to negative potential of non faradaic region), will plot current (half of the difference of forward and reverse current at middle of potential window) vs. scan rate and the slope will give CDL (double layer capacitance). Its unit is Farads. Is my understanding accurate??
Dividing CDL with specific capacitance of sample will give value of ECSA. How to obtain specific capacitance of sample??? My sample is thin film metal oxide coated on conductor.
RF = ECSA/Area of electrode.
Area of electrode is 1 cm2. So in that case ECSA wil be equal to RF with no unit.
What is specific current density how to calculate it?
Thank you in advance.
Dear Noorulain,
Your understanding to calculate Cdl is correct. However, the faradic contribution due to specific adsorption cannot be neglected within this narrow potential range. It depends on the electrolyte composition, pH and temperature etc. Also the selection of scan rate can significantly influence the kinetic response of the surface e.g. consider the IR drop.
I think you should use RDE for precise measurements.
Once you get the Cdl from CV analysis and if you know the thickness and dielectric constant of the film you may get directly get the ECSA.
The specific capacitance is the capacitance per unit mass (F/g) of the active material. This is not the F/cm2. If you know the deposited mass of the active material (thin film material) you can calculate specific capacitance.
The specific current and current density are two different terms, where the former is current/mass of the active material and the later is Current/area. The current density is of two types geometric (based on geometrical surface area) and true (based on electrochemical surface area).
For you information the Cdl can also be measured from EIS analysis and in this way you may validate the CV results. I hope i answered the question, if you want more information, please don't hesitate to contact me.
Thanks
Dear Noorulain,
Your understanding to calculate Cdl is correct. However, the faradic contribution due to specific adsorption cannot be neglected within this narrow potential range. It depends on the electrolyte composition, pH and temperature etc. Also the selection of scan rate can significantly influence the kinetic response of the surface e.g. consider the IR drop.
I think you should use RDE for precise measurements.
Once you get the Cdl from CV analysis and if you know the thickness and dielectric constant of the film you may get directly get the ECSA.
The specific capacitance is the capacitance per unit mass (F/g) of the active material. This is not the F/cm2. If you know the deposited mass of the active material (thin film material) you can calculate specific capacitance.
The specific current and current density are two different terms, where the former is current/mass of the active material and the later is Current/area. The current density is of two types geometric (based on geometrical surface area) and true (based on electrochemical surface area).
For you information the Cdl can also be measured from EIS analysis and in this way you may validate the CV results. I hope i answered the question, if you want more information, please don't hesitate to contact me.
Thanks
Again Kashif Mairaj Deen answered it best. Also you should know the deposited mass of your active materials
Dear Sir Kashif,
If i divide the Cdl by specific capacitance [F/g] which is different from areal capacitance [F/cm2]. In many papers the researchers described the Cs as F/cm2. Than how to satisfy the dimensions of ECSA? will be in g??
Dear Noorulain,
In the literature mostly the F/cm2 is based on the dimensional area of the electrode. The true surface area can be calculated by other characterization methods e.g. BET surface area measurement etc. But again this true area would not be similar to ECSA as not all the micropores are accessible to the electrolyte which should account for high capacitance.
You may either use dimensional electrode area or may calculate the ECSA as i mentioned in my previous reply.
Thanks
@Sir Kashif @Sir Gabi thanks much fro you valuable suggestions. Its really helpful.
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