**3.5 Catalyst/conductive substrate engineering**

The notable drawbacks of non-noble metal/oxide-based electrocatalysts are their poor electrical conductivity and their agglomeration during the catalysis process, which limit their bifunctional catalytic performance in oxygen electrocatalysis. The succeeding forward step to resolve these issues is the decoration of catalyst materials over the highly conductive substrate, which simultaneously limits the agglomeration and improves the electrical conductivity. Carbon-based materials are promising candidates that serve as a substrate by providing a facile electron transfer path and flat facets to adhere catalytically active non-noble metals/oxides. Moreover, non-noble metal/oxide-based electrocatalysts are efficient candidates for OER and not for ORR, which is another remarkable drawback; meanwhile, carbon-based materials are demonstrated to be effective catalysts for ORR. When combined, these two materials can effectively catalyze both the oxygen electrode reactions without any interruption due to synergistic effect, where the ORR part is taken care of by carbon-based materials and the OER part by catalytically active non-noble metal/oxide. So, again hybrid material (catalyst/carbon substrate) engineering is the solution, which resolves the ORR activity issue along with electrical conductivity and agglomeration issues. But carbon materials are prone to oxidize in highly positive OER overpotential regions, causing thermodynamic instability as another issue. Hence, it is determined that the

*A Perspective on the Recent Amelioration of Co3O4 and MnO2 Bifunctional… DOI: http://dx.doi.org/10.5772/intechopen.109922*

hybrid material (catalyst/carbon substrate) engineering is an effective strategy to proliferate electrical conductivity and ORR activity. However, proper selection of carbon-based substrates (stable at higher positive overpotentials) and feasible way of incorporation lead to better catalytic performance and durability.

Therefore, in this section, all the in-built possessions of the catalyst materials and their impact on their properties have been elaborately discussed and the possible ways of fine-tuning them for the improvement of bifunctional catalysis are also suggested. This collective knowledge ignites the interest of the research community to formulate efficient bifunctional catalysts and take them to the next level.
