How the pseudocapacitance will arise Which functional group should contribute much to it?
First of all, I shall point out that the question you asked has not yet a comprehensive and clear answer in the literature. Every one just postulates that the oxygen containing groups (such as carbonyl, carboxyl, ether and epoxy groups) in graphene (and other carbonaceous materials) are redox active, and hence would contribute to charge storage via the pseudocapacitance mechanism. However, no evidence has been reported that can correlate directly and convincingly the amount of charge stored and the number and nature of the oxygen containing groups (OCGs).
On the other hand, the redox activity of these OCGs should also depend strongly on the nature of the electrolyte, i.e. if the electrolyte is aqueous or non-aqueous because the redox reactions of the OCGs is highly likely involving the participation of protons or water. In other words, they are pH dependent.
Ionic liquids, such as the one you used, is non-aqueous, and hence contain very limited amounts of protons/water. They are therefore not good for promotion of the redox activity of OCGs. However, they may still show capacitance higher than that expected from the EDLC or the known specific surface area. There is not yet a proper answer in the literature.
We are the first to account for the pseudocapacitance of reduced graphene oxides (RGOs) by the transfer of delocalized valence electrons, instead of the redox activity of OCGs. In our explanation, the OCGs are not contributing to charge storage via their redox reactions, but that they can restrict the degree of electron delocalization and hence contribute to pseudocapacitance. Note that not only oxygen atoms, but doping graphene by other heteroatoms should also lead to restriction of the degree of electron delocalization and hence to pseudocapacitance. You may read our recent publication for more information.
https://doi.org/10.1039/c7cc04344a
Last, but not the least, the question you asked is not new, and the answer is not simple. More specifically, you may be able to correlate the specific surface area, oxygen content and specific capacitance (or charge capacity) of your RGOs, and the results may then tell you better if there is a significant level of pseudocapacitance.
Dear Debasis,
I strongly advise to back of the following article as an answer for your quation with more details.
Regards,
First of all, I shall point out that the question you asked has not yet a comprehensive and clear answer in the literature. Every one just postulates that the oxygen containing groups (such as carbonyl, carboxyl, ether and epoxy groups) in graphene (and other carbonaceous materials) are redox active, and hence would contribute to charge storage via the pseudocapacitance mechanism. However, no evidence has been reported that can correlate directly and convincingly the amount of charge stored and the number and nature of the oxygen containing groups (OCGs).
On the other hand, the redox activity of these OCGs should also depend strongly on the nature of the electrolyte, i.e. if the electrolyte is aqueous or non-aqueous because the redox reactions of the OCGs is highly likely involving the participation of protons or water. In other words, they are pH dependent.
Ionic liquids, such as the one you used, is non-aqueous, and hence contain very limited amounts of protons/water. They are therefore not good for promotion of the redox activity of OCGs. However, they may still show capacitance higher than that expected from the EDLC or the known specific surface area. There is not yet a proper answer in the literature.
We are the first to account for the pseudocapacitance of reduced graphene oxides (RGOs) by the transfer of delocalized valence electrons, instead of the redox activity of OCGs. In our explanation, the OCGs are not contributing to charge storage via their redox reactions, but that they can restrict the degree of electron delocalization and hence contribute to pseudocapacitance. Note that not only oxygen atoms, but doping graphene by other heteroatoms should also lead to restriction of the degree of electron delocalization and hence to pseudocapacitance. You may read our recent publication for more information.
https://doi.org/10.1039/c7cc04344a
Last, but not the least, the question you asked is not new, and the answer is not simple. More specifically, you may be able to correlate the specific surface area, oxygen content and specific capacitance (or charge capacity) of your RGOs, and the results may then tell you better if there is a significant level of pseudocapacitance.
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