it is reported that "The absence of redox peaks indicates that the supercapacitors are charged and discharged at a pseudo-constant rate over the entire
voltammetric cycles"
Nat. Nanotechnol. 2011, 6 ( 4) 232– 236
Nano Lett., 2012, 12 (1) 321–325
I would like to understand what does this statement mean ? and why the configuration of CV is different between 3 and 2 electrodes systems ?
Thanks in advance
As Artur has explained, peaks in the CV indicate a redox process occurring on the electrode. These are often not 100% reversible so are likely to deteriorate with time. A square shape in the CV is indicative of charge build up following a electric double layer capacitance (EDLC) mechanism.
The 3-electrode system is helpful for determining the capacity of very small amounts of materials and if you do not have the facilities to prepare coin cells of your materials - just make sure that the surface area of your counter electrode is much greater than your working electrode.
A good source of information for capacitance measurements can be found here: Energy Environ. Sci., 2010,3, 1294-1301 (not my work)
Dear all,
Thanks for your very useful discussion.
I really confused after reading the enclosed paper (find attached paper, page 5) which showed the difference CV in case of 3 and 2 electrodes systems in the same electrolyte and the author claim that reason " The absence of redox peaks indicates that the supercapacitors are charged and discharged at a pseudo-constant rate over the entire voltammetric cycles" and he cited the papers that i have mentioned before.
They used Co3O4 which exhibited a psedocapacitance redox couples in 3 electrodes but only exhibited a rectangular shape in 2 electrode system .
If all of you have comments, it is welcome you to share them with me
Thanks
Saad
Dear Mohamed it's a common phenomena. In 3 electrode system, potential of the working electrode is clearly defined , wherein case of 2 electrode system, potential is measured between the two electrode and thus potential will be different from that of 3-electrode system. and further current also becomes averaged depending on the voltage of the either electrode.
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