Eco-Friendly Mechanochemical Synthesis of Bifunctional Metal Oxide Electrocatalysts for Zn-Air Batteries.

The development of green and environmentally friendly synthesis methods of electrocatalysts is a crucial aspect in decarbonizing energy generation. In this study, eco-friendly mechanochemical synthesis of perovskite metal oxide-carbon black composites is proposed using different conditions and additives such as KOH. Furthermore, the optimization of ball milling conditions, including time and rotational speed, is studied. The mechanochemical synthesis in solid-state conditions without additives produces electrocatalysts that exhibit the highest bifunctional electrochemical activity towards both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Moreover, this synthesis demonstrates a lower Environmental Impact Factor (E-factor), indicating its greener nature, and due to its simplicity, it has a great potential for scalability. The obtained bifunctional electrocatalysts have been tested in a rechargeable zinc-air battery (ZAB) for 22 h with similar performance compared to the commercial catalyst (Pt/C) at significantly lower cost. These promising findings are attributed to the enhanced interaction between the perovskite metal oxide and carbon material and the improved dispersion of the perovskite metal oxide on the carbon materials.