Dear All,
I am trying to calculate specific capacitance of my Metal Oxide electrodes such as NiOx, AuOx, PtOx etc. From detailed discussion in literate I found following equation.
Equation 1.
Csp= Area under the CV curve/2(scan rate x voltage window x mass of the material)
In a typical CV we observe Faradaic regions including OER, HER, Metal redox reaction region some what in between OER and HER and non-faradaic region.
My question is for specific capacitance measurements what should be optimal potential window?
In some papers researchers are using metal redox region of CV later on integrating it, Some used metal redox region for metal oxide electrodes after subtracting oxidation and reduction peak integration from overall CV (redox region) integration.
I wonder why they are choosing redox region of CV???
Can we just use non-faradaic region rather than subtracting faradaic peak integration from total E/I integration curve?
Please give some details on selecting capacitive or charge accumulation region from CV curve.
Thank you in advance.
dear Noorulain Babar; I think it's better to make electrochemical Impedance Spectroscopy (EIS) measurement to evaluate the behavior of the oxidize sample and to calculate the capacitance. you can read https://www.wiley.com/enaf/Impedance+Spectroscopy%3A+Theory%2C+Experiment%2C+and+Applications%2C+2nd+Edition-p-9780471647492.
I wonder which applications for the specific capacitance you would like to calculate? (e.g. in supercapacitor, or catalyst's evaluation for OER or HER).
Hello,
when it comes to testing of supercaps, the new Gamry whitepaper is sure to be very interesting. It covers both EIS and CV.
https://www.gamry.com/assets/Uploads/resources/Final-Gamry-Testing-Super-Capacitors-Final.pdf
Best regards,
Andreas
Hi Babar,
For case of OER and HER, CV curves of catalysts can be examined with different scan rates in non-faradic area for measuring the double layer charging, from which could be used to calculate the electrochemically active surface area. (1,2)
In case of supercapacitor, the window potential chosen for supercapacitor can be contained oxidation/reduction processes of electrodes due to that are reversible processes, but should not be included irreversible process such as HER or ORR. Hence, the potential window should be optimized by CV before doing other things for specific capacity, energy and power density calculation.
(1) https://pubs.rsc.org/en/content/articlehtml/2017/cc/c7cc01489a
(2) Article Synthesis of Water-Dispersible Single-Layer CoAl-Carbonate L...
Thank you all for valuable response.
Dear Tran Thanh-Nhan , I am not sing electrode for water splitting or as capacitor specifically. I have prepared few electrodes as nano-sensors (electrochemical sensors) and want to see how much charge is getting accumulated at the inter phase electrolyte/catalysts, and effect of scan rate on charge accumulating property and specific capacitance of electrode. I think i should choose redox reversible region as I am not studying HER and OER.
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