Anchoring Mn₃O₄ Nanoparticles on Oxygen Functionalized Carbon Nanotubes as Bifunctional Catalyst for Rechargeable Zinc-Air Battery

Transition metal oxide hybridized with carbon is promising for multifunctional electrocatalysis. In this work, Mn₃O₄ nanoparticles were embedded into oxygen functionalized carbon nanotubes (Mn₃O₄/O-CNTs) via a facile wet impregnation method followed by oxygen plasma treatment. The O-CNTs not only act as conductive support for Mn₃O₄ nanoparticles, but also provide catalytically active centers for the oxygen evolution reaction (OER). This material benefitted from both the excellent electrocatalytic activity and the separated oxygen reduction reaction (ORR) and OER active sites, as the zinc-air battery assembled from the bifunctional Mn₃O₄/O-CNT electrode exhibits high power density, reaching 86.6 mW cm^-2 with discharge capacity up to 827.6 mAh g^-1 and super cycling stability, which can be stably charged and discharged over as long as 150 h at 2 mA cm^-2. Our work demonstrates an innovative design for stable bifunctional catalysis in renewable energy applications.