I tried to figure out the overpotential term that exists in MECs. Going through the literature to find a sensible meaning, I understood that it should be defined based on the specific electrochemical cell that we are working on it. Does this mean the potential difference between the theoretical and actual potential that is needed to form Hydrogen? Should it be calculated for each half cell separately? What are the sources of these overpotentials? Do you choose a metal catalyst because of the low activation overpotential for gas products (H2) evolution reaction? How is it possible to discuss an overpotential when the metal catalyst is replaced with a biocatalyst?
Yes, the overpotential of any reaction is the difference among the theoretical and the actual determined value and it depends on the different experimental conditions you used, as the cathode composition, the stirring rate or the electrolyte pH. Then, if your purpose is the hydrogen generation you will diminish this overpotential in order to decrease the operation cost.
Although I know nothing about biocatalyst, I think that you can also discuss the different results obtained with the different catalyst tested without problems.
Thanks Jordi Carrillo Abad .....by what I understood from ur text, my experimental condition is also a source of overpotential. Would you refre me to any aricles bout this matter if you keo any? what about my electrodes. When I went through the literature, I have found some values for activation overpotential for graphite, and precious metal. This values are the reason of loading electrodes with these metal catalyst, I mean the reason is activation overpotential?
Some of my workmates are working on hydrogen production in alkaline media by means of electrodeposited electrodes. This is one of their papers and I hope that it will help you:
http://www.sciencedirect.com/science/article/pii/S0378775313008197
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