Thanks for your clarifications Dr. Braun.

My main concerns come into the mathematical aspect of the terminology.

Regards

Jaime Sanchez

At the last ISEE cap there was even a strong discussion between Jean-Michel Saveant and Yuri Gogotsi about this topic.

There is always the question what name to put for a certain observation.

On the spectrometric side some d-Metals might give the same electrochemical responses (e.g. CVs) as an activated carbon.

This, however, are the currents and the voltages one measures and the capacities and capacitances he interpretes out of the spectra.

With a typical potentiostat setup we may not look on top of the surface and we may not understand the "real" electrochemical process, we are just guessing which type of reaction occurs to the best of our knowledge.

For pseudocapacitive processes this is exactly the case. From our knowlegde we know that a certain material undergoes faradic reactions, in our CV we observe however a capacitive behaviour.

And now we are at the beginning of the big discussion:

Do we want to name the effect? (Pseudocapacitance)

Or do we want to name the cause? (Interfacial faradic reaction)

And then there are studies in which a battery material, that may show pseudocapacitance in a certain arrangement (Voltage window; thickness of the film etc.), is taken, but in this particular study it features the properties of a battery material. These studies are often poorly conducted and neglect the prior discussions on pseudocapacitance.

Mathematically speaking, I would calculate the capacitance for a capacitive and also for a pseudocapacitive material. For a battery material with an unique charge/ discharge profile also shown in the above mentioned publication, I would calculate the capacity.

Dear Lars Henning Heß,

I have considered the topic as a hot topic in the field of aqueous hybrid/supercapacitor energy storage systems, that is one of the reasons i have brought here in order to clarify and shed some light into the scientific discussions.

As you already well mentioned mathematically speaking, we are able to compare our capacitives (nanoestructured carbons, activated carbons, graphenes, CNT..) and pseudocapacitive materials (RuO2, MnO2, MXenes..) in F.g-1, but this value is an average value calculated over a limited potential window, so constant in the whole range. However in our battery-type materials (Oxides and hydroxides here mentioned) or nanocomposites with certain percentage of this oxides only the capacity in C.g-1 or mAh.g-1 provides a consistent metric because of the non-linear dependance of the charge stored vs the potential window.

Thanks for sharing your personal view.

Regards

Jaime