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Look for my error in computing the Nernst Potential of PEM fuel cell

Look for my error in computing the Nernst Potential of PEM fuel cell

Look for my error in computing the Nernst Potential of PEM fuel cell

I am trying to compute the Nernst Potential of a 80C (353K) PEM fuel cell operating at 1 bar (100 kPs). I am going to be operating the cell with pure H2 and ambient air (not pure O2). The standard pressure Nernst potential at 80C is 1.18 V.

Since I am operating with pure H2, then I assumed the mole fraction of that is 1 and the mole fraction of the oxygen is 0.21 since air is 21% oxygen.

When I went to go calculate the nernst Potential, I am getting something above the standard nernst potential which shouldnt be happening. The calculation I am using is

E = E0 + (R*T/2F)*ln(PH2*sqrt(PO2)/PH2O)

With the mole fractions, the partial pressures of H2, O2, and H2O are 100 kPa, 21 kPa, and 100 kPa, respectively. I keep getting a Nernst potential of 1.20 V which is higher than the standard Nernst Potential

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