In this study we have closely examined the interplay between photogeneration and transport of holes and water oxidation reactions on a TiO2 surface. As noted in the introduction, there are several possible factors responsible for the overall low efficiency of the water oxidation reaction including hole trapping by surface defects and impurities leading to low mobility and high recombination rates that prevent holes from reaching the reaction sites. A comparison of the calculated photo-OER kinetics to the experiments provides some information on these factors and raises additional questions.