Nowadays the development of low-cost, earth-abundant, non-toxic, noble metal-free, and highly efficient electrocatalysts for the sluggish oxygen evolution reaction (OER) remains one of the most difficult challenges to ultimately be faced to achieve efficient water splitting for the hydrogen production (energy carrier and clean chemical fuel). OER occurs at the anode in water-splitting electrochemical cells, it is more complicated than the hydrogen evolution reaction (HER). It involves the four electrons transfer coupled with O-O bond formation, and cleavage of the O-H bond compared to HER. Thus, this reaction needs higher overpotentials to overcome high kinetic energy barriers and, for this reason, the use of electrocatalysts is envisaged to accelerate the reaction kinetics and reduce the energy barrier.