This is a CV curve of VACNT supercapacitor electrode. There is an initial dip in the current during charging as well as discharging after which the current rises steeply. What could be the reason behind this non-capacitive behaviour?
Interestingly, this was observed at 50mV/s, and when the scan-rate was reduced, the current rises sharply from the origin as usual.
Ideal (super)capacitors declares rectangular (model) CVs at sufficiently low (limit) scan-rates (
Thanks for the elaborate explanation, Ioannis Samaras I have observed the slope to change with increase in scan-rate as you can see in the figure attached. But what I have not observed is the initial dip previously at 50mV/s (pointed by red arrows in the figure in question). I have oxidized the samples with 0.2M HNO3 before doing CV with 0.5M KCL. Could this be the cause? Then why am I not seeing it at sower scan?
Yes[1], this is the chief reason.
Also, the dominant cause of that[2] initial dip should be an Ohmic drop (iR), because the early ('opening'[3]), short time[4], total (mixed) conductivity of a 'very fresh' WE is, usually, lower.
1. Quotation [Kingshuk]: "... I have oxidized the samples with 0.2M HNO3 before doing CV ..."
2. The initial dip at 50mV/s (pointed by red arrows in the figure in question).
3. After dipping a 'very fresh' WE in the cell, and before any actual cell-studies (CV, EIS, etc.), wait some hours, for some 'WE-sweating', in the electrolyte (of the cell).
4. Aging of a WE is another (very long time scale) class of studies.
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