**5. Recent exploration in Co3O4 and MnO2**

Transition metal oxides like manganese oxides α-MnO2 [37, 38], β-MnO2 [39], perovskite (i.e., LaNiO3, LaCoO3) [40] as well as spinel-based structures (Co3O4 and NiCo2O4) with multiple valences, serve as the most attractive non-precious metal catalysts for bifunctional OER/ORR electrocatalysis especially for the alkaline medium. This chapter particularly emphasizes the recent developments in metal oxides of manganese oxides and cobalt oxides, which are simple in composition yet very effective in promoting oxygen electrode reactions. The nature of active sites and their identification along with corresponding ORR/OER activities will be correlated with respect to their oxidation states, crystal structure, bulk structure and morphology with required experimental and computational analyses; all those concerns have been reviewed from the recent 10 years of literature. In addition to that, contrast results observed in those particular materials are discussed elaborately and possible strategies to further improve the activity of the catalyst have also been suggested at the end.
