Theoretical and experimental methods are adopted in order to gain further understanding of photocatalytic water splitting over the semiconductor TiO2. Periodic density functional theory calculations are used to study the adsorption of water on the rutile TiO2(110) surface. Results of studying the influence of acidic surface species on the energetics of the system are compared with new experimental measurements of the kinetics (using transient absorption spectroscopy) and photocurrent (photoelectrochemical set-up) as a function of pH.