Recently, zinc-air batteries have attracted increasing attention. These batteries exhibit high potential for many future energy applications because they offer high energy density at low cost. Besides, the batteries use zinc anode which is abundant, safe and non-toxic. However, their practical and extensive application is hindered by the sluggish oxygen reduction reaction (ORR). Thus, ORR electrocatalysts are employed to enhance the battery performance.

Noble metals such as platinum have played a dominating role as ORR electrocatalysts. Though they offer the advantages of high catalytic activity, electronic conductivity, and stability, their high costs are a serious concern. Therefore, much effort has been paid to metal oxides that are environmentally friendly and low cost. Among these, manganese dioxide (MnO₂) is recognized as a potential alternative because of its abundance, low cost, low toxicity, and efficient electrocatalytic performance. The catalytic activity of MnO₂ depended on the crystallographic structure and surface area. However, MnO₂ has low intrinsic electrical conductivity. Traditionally, MnO₂ coating on carbon supports is used to improve the electrocatalytic performance. Graphene, with its intriguing properties such as large surface area and high electrical conductivity, has recently received enormous attention as a possible candidate.

In this work, a cost-effective approach to synthesis MnO₂ nanoflowers decorated reduced graphene oxide is proposed. The ORR electrochemical performance of the synthesized catalysts was examined. The optimal loading ratio of MnO₂ is then determined. A zinc-air battery installed with the synthesized catalyst air cathode outperforms and exhibited a larger current density compared with the battery using a commercial Pt/C air cathode. Also, the results indicated that MnO₂ nanoflowers decorated reduced graphene oxide offers a promising and cost-effective air cathode for zinc-air batteries as well as other metal-air batteries.