The most critical challenges faced by human beings are shortage of green and sustainable energy. One of the most critical aspects of research has focused on the generation of clean and sustainable energy and storing these energies for further use. The European Union's, 8th EAP 2050 priority objective is to achieve climate neutrality in the union and aims to accelerate the green transition and restore the environment. It can be achieved by emerging new technologies in energy generation and storage systems. The battery devices that have aesthetic appeal and multi-functionality inspired the rapid development of sustainable energy sources. State-of-the-art commercial lithium-ion batteries have an energy density of 300 Wh kg-1, which falls short of the expected energy target i.e. 400 Wh kg-1. Metal-Air batteries (MABs) e.g. Li-O2 aqueous battery shows higher theoretical specific energy (3582 Wh Kg-1) and energy density (2234 Wh I-1); it is about 10 times higher than most batteries in the market today, but only two-fold improvements have been practically reached to date. Therefore, there is a lot of scope for the development of MABs. It has the capability to fulfill the energy demand rising from portable electronic devices, electrified transportation, and grid-scale applications as immersed by the European Battery Alliance. The most challenging issue in the development of MABs is the use of precious metal catalysts and insufficient catalytic activity toward the cathode catalysis. Therefore, we need to develop new cathode catalysts in the field of rechargeable MABs that are environmentally benign, safe, possess high energy density and long cycle life, and consist of low-cost materials.

Keywords
Metal-Air Batteries; OER; ORR; ZrN; NiCo LDHs; Galvanic Replacements; Kirkendall Diffusion; Engineered Morphology