Functional porous materials as bifunctional catalysts for metal-air batteries

Highly energy-dense metal-air battery (MAB) performance is mainly governed by the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) happening at the cathode interface. A suitable catalyst is required to enhance the kinetics of these two reactions and guide the reactions in a four-electron transfer reaction pathway. As a good ORR catalyst, high onset potential, low Tafel slope, high half-wave potential, and high limiting current are the criteria we should focus on; and as a good OER catalyst, the criteria are high onset potential, low Tafel slope, and low overpotential. Metal-organic framework (MOF), covalent organic framework (COF), and perovskite-type new-generation porous materials with high specific surface area, high pore volume , and less resistive pathway seem to have the benefits mentioned in required bi-functional catalysts for their application in MABs. Hence, in this review article, we have critically reviewed the recent developments in the mentioned functional porous materials as suitable bifunctional catalysts for metal-air batteries.