“…[1][2][3][4][5][6] Suitable electrocatalysts can play a significant role in minimizing the energy/overpotential, i. e., cost for water oxidation. In the last two decades, there has been significant research on the development of electrocatalysts, e. g., precious and nonprecious metal or metal oxide nanoparticles, e. g., Au, [7][8][9] Pt, [10] RuO x , [11] IrO x , [12] CoO x , [13][14][15][16] MnO x , [17,18] NiO x [19,20] nanoparticles, and metal complexes, e. g., copper and cobalt complexes. [21,22] Among the mentioned electrode materials, CoO x including Co 3 O 4 and CoO, have been investigated vigorously due to its high efficiency, low cost, low toxicity, and wide availability all over the world.…”