MnCo₂O₄/Mn₂O₃ Nanorod Architectures as Bifunctional Electrocatalyst Material for Rechargeable Zinc–Air Batteries

Abstract

Recently, the demand for stable, cost-effective, and highly active bifunctional catalysts has increased in the energy storage community. In this study, we present the preparation of manganese cobalt oxide/manganese oxide (MnCo 2 O 4 /Mn 2 O 3 ) nanorod (NR) materials via a facile one-step hydrothermal method without calcination. The MnCo 2 O 4 /Mn 2 O 3 NR revealed better electrocatalytic properties toward the oxygen reduction and oxygen evolution reactions. The MnCo 2 O 4 /Mn 2 O 3 NR electrocatalyst exhibited high diffusion-limiting current density values and greater durability compared to the Pt/C and IrO 2 catalysts, respectively. The electrode material showed excellent chronopotentiometric stability for 30 h at 10 mA cm −2 and displayed remarkable stability at different current densities with low potential drops. Furthermore, the MnCo 2 O 4 /Mn 2 O 3 NR-based zinc−air battery (ZAB) exhibited a slightly smaller voltage plateau as well as lower electrochemical impedance values than the Pt/C//IrO 2 -based ZAB. Significantly, the MnCo 2 O 4 /Mn 2 O 3 NR-based ZAB (68 cycles @ ∼ 20.3 h) demonstrated better durability than the Pt/C//IrO 2 -based ZAB (28 cycles @ ∼ 8.3 h). The obtained excellent bifunctional catalytic properties and cycling stability results indicate that MnCo 2 O 4 /Mn 2 O 3 NRs are cheap and promising bifunctional catalyst candidates for rechargeable metal−air batteries.