For the late transition metal oxides, CaCoO 3 and CaNiO 3 , the free energy required for the initial oxidation step exceeds that of the solvated hydroxyl radical (∆G• OH(aq) = 2.4 eV) by 0.2 and 0.1 eV, respectively. This suggests that, upon formation of surface-bound OH * , there is a thermodynamic preference for the species to either desorb as a solvated hydroxyl radical or recombine on the surface to form a hydroxyl group. In the second oxidation step of water oxidation, CaCoO 3 exhibits comparable energetics for the formation of both metal-oxo species and hydrogen peroxide, leading to the coexistence of these products. In contrast, CaNiO 3 stabilizes the metal-oxo intermediate with an energetic preference of approximately 0.2 eV, favoring the pathway toward oxygen evolution reaction (OER) over hydrogen peroxide formation.