The development of effective water oxidation catalysts (WOCs) is of central importance to multiple green energy technologies. Water oxidation is not only key in the splitting of water to oxygen and hydrogen, Equation 1, but also in the reduction of CO2 by water, Equation 2, and other targeted processes. The research community is investigating fuel producing reactions such as Equations 1 and 2 under electrochemical, photolytic, photoelectrochemical, and thermal conditions, that is, where “energy” in Equations 1 and 2 is an applied potential, light, an applied potential plus light, and heat, respectively. Not surprisingly given these points, there has been a great deal of recent research on the catalytic water oxidation problem and WOC development.