The water splitting reaction provides a convenient process through which intermittent renewable energies are stored in the form of chemical fuels, namely hydrogen and oxygen . Although numerous transition metal oxides have been explored as catalysts for the oxygen evolution reaction (OER, 2H2O → O2 + 4H + + 4e -) , this reaction remains a bottleneck in the water splitting reaction. While only precious IrOx, RuOx, and their composites have sustained OER activity in acidic solutions, a number of non-precious metal oxides are reported to have higher activity than IrOx in alkaline solutions.