Iron oxide, in particular a-Fe2O3 hematite has been investigated as model photoanode for solar water oxidation for many decades. We have investigated this material with soft x-ray spectroscopy methods and found some chemical changes at the surface when the material is operated as photoelectrode. The first observ ation is that the surface is sub-stoichiometric; it contains an Fe2+-enriched surface. Under anodic bias, the Fe2+ becomes converted to Fe3+ with a parabolic growth law. Also, hole doping is observed on the same samples. Additionally, the surface appears to become hydroxylated or oxy-hydroxylated. The relative abundance of the OH or OOH groups increases with increasing bias potential to the point where the water oxidation sets on. At higher potentials, the surface groups disappear gradually. In the same course, the hydrogen bonds which hold water molecules together become increased and decreased. We have also done in situ and operando experiments which show a nice parallel process of photo hole formation and delection depending on the applied bias. We are therefore able to sketch a realistic scenario of physics and chemistry going on at the surface and subsurface during water oxidation.