Hello everyone!
I'm working on the electrosynthesis of polymer film based on metallo-porphyrin (in fig 1). For the polymer synthesis, I'm performing cyclic voltammetry using a solution prepared in ACN with TBAP as supporting electrolyte.
The resulting voltammogram is shown in figure 2.
From this, it seems that the polymer is conductive with an increase in the current cycle by cycle.
I'm trying to characterize the polymer in a solution of a redox probe (e.g. [Fe(CN)6] 3-/4- prepared in water with KCl as supporting electrolyte ), by cyclic voltammetry. The comparison between the bare electrode and the functionalized electrode with polymer shows a dramatical decrease in current after the electropolymerizationpolymerization.
How is it possible to describe this different "behaviour" of the film?
Any useful papers?
Thank you!
Tiziano
Electrical conductivity is due to the movement of charge in response to an electric field where as Ionic conductivity is an electrical conductivity due to the motion of ionic charge.
Dear Sir,
From your results it seems your film hinders faradaic current.
Have you tried EIS (Electrochemical Impedance Spectroscopy) ?
Best regards,
Nicolas Murer
Dear Professor Madhukar Baburao Deshmukh , thank you very much for your quick reply. Yes, it's true, but, is it possible for a polymer to be electronically conductive but extremely non-conductive ionically?
I know that for films for which an aniline-like polymerization mechanism is assumed, an increase in electronic conductivity can be observed as polymerization proceeds (increase in oxidation and reduction currents), whereas it is unclear what generally happens to ionic conductivity. Works about a characterization of this kind of film with a redox probe, could be very useful for me....
Dear Dr Nicolas Murer , thank you very much for your kind reply. Yes, I did it! Impedance data goes in the same direction as cyclic voltammetry data. How is it possible to explain the decrease in faradaic current using a redox probe?
Dear Tiziano Di Giulio , first of all your EIS graphs should be orthonormal... https://www.biologic.net/topics/nyquist-plots-why-use-the-orthonormal-scale/
And yes as you said, it confirms cyclic voltammetry data: the deposited films are only capacitive. It is hard what you have with the bare electrode... do you see a Warburg behaviour at low frequencies ? What is the value of the low frequency ?
Best regards,
Nicolas Murer
Dear Nicolas Murer, thank you very much for your reply.
I'm showing you the Nyquist plot for the bare electrode and the data fitting with a Randles circuit. It seems that there is a Warburg component in the impedance spectrum. Is it an useful information?
Tiziano Di Giulio Thanks for this. Well, it means the process on the bare electrode is a typical redox process with diffusion limitation. For some reason, the deposited film hinders this process...
The increased current density is due to the movement of the free electrons and it can be also due to the electron transition in the conjugated system in response to the electric field.
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