We will now discuss the consequences of the calculated free energy diagram in Fig. for the remaining Ca perovskites with respect to their suitability as OER catalysts. The calculated free energy diagram demonstrates that CaVO 3 might act as an effective catalyst for oxygen evolution. The adsorption of hydroxyl species (∆G OH * = 1.4 eV) on CaVO 3 is well documented, with its free energy significantly lower than that associated with the formation of hydroxyl radicals.