MnCo<sub>2</sub>O<sub>4</sub>/Mn<sub>2</sub>O<sub>3</sub> Nanorod Architectures as Bifunctional Electrocatalyst Material for Rechargeable Zinc–Air Batteries
Ramakrishna Reddy Ayyaluri, B. N. Vamsi Krishna, Obula Reddy Ankinapalli, Young Jun Lee, Logeshwaran Natarajan, Jae Su Yu
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.