Tracing a pe-Ph plot at 90°C I was wondering if there is no problem with the stability limit of water with Hydrogen. It not seem to be consistent with the database used. In my example, I used Thermoddem database from BRGM but when calculating the equation of the line, there is a mistake. In particular there seems to have a problem between the logK of the H2/H+ reaction and the equations which should be pe=-logK / 2 - pH for H2(g) = 2H+ + 2e- and for a H2 fugacity of one bar. However it seems to miss the minus of log K and the absolute value seems not to be the good one if you take an other database than the default one. When plotting a reaction path in this diagram where H2 and H2O co-exist, the dots do not follow the equilibrium line and are in the stability field of H2 which seems to confirm the problem.
Thanks for your help