In fuel cell electrochemical calculations, when we subtract the concentration from potentials, do we need to subtract the absolute values of the concentration losses or the values themselves from E0?
This might help:
http://ecpower.utk.edu/Publications/docs/An%20Introduction%20to%20Fuel%20Cells%20and%20Related%20Transport%20Phenomena.pdf
Looks like concentration polarization losses and activation polarization losses occur separately at the anode and the cathode, and resistive losses are throughout. I think you are asking whether these loss values are always strictly subtracted from E0 (open circuit potential), because sometimes the expressions for these losses are positive (activation) while sometimes they appear negative (concentration)?
Whatever it takes to reduce the E0 value, would seem the logical answer.
In V-I plot, the dependance of Voltage with current denisty varies throughout the regime of currenet denisty depending on the polarization loses viz. charge transfer, ohmic, concentration /diffsuin etc. In majority, the dependence is non-linear. Therefore, merely subtracton in any portio could lead to erronius results. The behavour of the specific sample has to be understood with reference to current density.
I think this was the confusion. The folowing link could be of help:
http://www.sciencedirect.com/science/article/pii/S0167273812006704
Cheers,......
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