Hi,
I have a semiconductor system that I am using to understand electroreduction reaction. Can I use Mott-schottky plot to comment on the n-type/p-type behavior of the system?
My worry is that I did not come across any paper on electrochemistry where they are using mott-schottky analysis to comment on the same. However, there are lots of paper in photoelectrochemistry. Can this analysis be applied to electrochemistry too?
Thanks,
Saurav
See, for example:
http://www.abc.chemistry.bsu.by/vi/Mott-Schottky.pdf
Dear Saurav Ch.S.,
the question of existence , non-existence of Mott-Schottky type of response in electrochemistry is more complicated than is the case in simple crystalline semiconductors, where the majority mobile carriers are either electrons and/or holes, both of which can move "freely" across the metal electrode-semiconductor interface. There, the only relevant parameter is the difference in the electrochemical potential of electrons(holes) in the bulk of the semiconductor and in the metal electrode. This difference determines the amount of mobile charge (again, electrons or holes) to be transferred across the interface and in this way, it is directly related to the bulk density of these charges.
In the electrochemical cell, the situation is quite different.
Firstly, it is seldom that the majority mobile charges are electrons or holes here (usually, they are ions of one type or the other). This means that the usual Mott-Schottky formula for dc bias dependence of the "depletion capacitance" Cdepl(dc bias) can not be used without further analysis.
Secondly, the charge state of the interface is determined by the redox reactions , caused by finite electron transfer from and to the metal electrodes. Without knowing these reactions, the results for Cdepl(dc bias) can be easily misinterpreted.
The easiest approximation would be to assume blocking contacts, that is to say that there is no dc current across the interface. In this case, the mobile electrical charges, let us say some ions, will tend to screen the externally applied voltage through Debye screening and the Cdelpl(dc bias) becomes in fact Cdebye (dc bias), leading to sqrt(density of mobile charges) dependence.
With best regards
Petr
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