Reduced Graphene Oxide decorated with Manganese Cobalt Oxide as Multifunctional Material for Mechanically Rechargeable and Hybrid Zinc–Air Batteries

Spinel MnCo₂O₄ nanoparticles on nitrogen‐doped reduced graphene oxide (MnCo₂O₄/NGr) are synthesized for advanced zinc–air batteries with remarkable cyclic efficiency and stability. The synthesized MnCo₂O₄/NGr exhibits good oxygen‐reduction reaction (ORR) activity with half‐wave potential E _1/2 of 0.85 V (vs reversible hydrogen electrode (RHE)), comparable to commercial Pt/C with E _1/2 of 0.88 V (vs RHE) along with superior oxygen electrode activity ΔE = 0.91 V for the ORR/OER (oxygen‐evolution reaction) in alkaline media. Durability tests confirm that MnCo₂O₄/NGr is more stable than Pt/C in alkaline environment. MnCo₂O₄/NGr functions with stable discharge profile of 1.2 V at 20 mA cm^?2, large discharge capacity of 707 mAh g^?1_Zn at 40 mA cm^?2 and a high energy density of 813 Wh kg^?1_Zn in a mechanically rechargeable zinc–air battery. The electrically rechargeable MnCo₂O₄/NGr zinc–air battery displays hybrid behavior with both Faradaic and oxygen redox charge–discharge characteristics, operating at higher voltage and providing higher power density and excellent cyclic efficiency of 86% for over 100 cycles compared to Pt/C with efficiency of around 60%. Moreover, hybrid zinc–air battery operates with a stable and energy efficient profile at different current densities.