The oxygen evolving process is generally perceived as four one-electron oxidation steps each accompanied by a concomitant proton transfer. Yet the exact mechanism is a complex topic of much debate. A simplified view is that the reaction mechanism in large part follows one of three reaction types . The most common one, which is generally used as a foundation for the computational screening of prospective oxygen evolving catalysts conforms to a Volmer-Heyrovsky type of mechanism and can be described as a sequence of four consecutive concerted one electron/proton transfer reactions as outlined in eqs. :