Effect of Manganese oxide with its discrete valencies on Fe2O3/C to form (MnOx-Fe2O3/C) hybrid nanocomposite electrodes for enhanced ORR activity

Abstract

Electrocatalysts play a vital role in recently emerged energy conversion devices. The present study has been undertaken to synthesize non-precious metal oxides, i.e., manganese oxide-iron oxide/carbon (MnOx-Fe2O3/C) hybrid nanocomposites, as high-performance electrocatalysts for the oxygen reduction reaction (ORR). The synthesis involved a simple and low-cost co-precipitation method, where MnOx (MnO2, Mn2O3, Mn3O4) served as dopants to Fe2O3 supported on carbon derived from chitosan. The biopolymer-derived carbon provided a highly conductive framework, facilitating uniform dispersion of metal oxides and enhancing electron transfer. The Physiochemical and electrochemical investigations carried out via XRD, Raman, SEM/EDX, Cyclic Voltammetry (CV), Linear scan voltammetry (LSV) and Chronoamperometry (CA) revealed that MnO2-Fe2O3/C exhibited superior ORR activity with higher current density, lower onset potential, fast kinetics, excellent methanol tolerance and stability as compared to other samples tested. The synthesized MnO2-Fe2O3/C nanocomposite offered lower charge transfer resistance (Rct) and elevated electrocatalytic efficiency when subjected to electrochemical impedance spectroscopy (EIS). The enhanced ORR performance of the MnO2-Fe2O3/C composite might be attributed to the synergistic interaction between MnOx and Fe2O3 along with the conductive behavior of the chitosan-derived carbon matrix. These findings demonstrate that MnO2-Fe2O3/C is a promising non-precious metal electrocatalyst for ORR, offering a sustainable, low-cost alternative to noble metal catalysts for fuel cells.