Under what temperature, pressure, and concentration?
Oxygen molecules, atoms, or ions?
Hydrogen molecules, atoms, or ions?
Double-check your rate constants, not just equilibrium constants...
Over much less than geological timespans, free oxygen in planetary environments goes away. Yes, you'll get atomic oxygen forming above the atmosphere as UV breaks water molecules down, but that is a very miniscule fraction of the oxygen bound up in the whole syste,.