In this work we take the mechanism reported by Wang et al. for rutile TiO2 and integrate it with a simple 1-D array model for the single crystal TiO2 photophysics to simulate the full photo-OER process in this system. We have focused on evaluating the correlation of hole densities and spatial distributions and the extent of hole diffusion on the TiO2 surface with the overall reaction rate and the kinetics. In particular, we examine the effect of hole mobility at the surface in order to assess whether freely diffusing holes result in different kinetics than holes that are stationary, for example when deep traps (which can be surface polarons) are involved. The results show that the trends with light intensity are complex, with hole formation and diffusion in the bulk crystal dominating the chemistry at low intensity, then becoming nearly independent of light intensity in the upper range where buildup of intermediates that participate in thermal reactions becomes important. Comparisons with experimental observations of a high order dependence of rate on hole concentrations suggest that the TiO2 structure (e.g. single crystal vs nanocrystal aggregate) may play a role in the apparent kinetics.