Chitosan‐Derived NiO‐Mn ₂ O ₃ /C Nanocomposites as Non‐Precious Catalysts for Enhanced Oxygen Reduction Reaction

Abstract

Abstract NiO‐Mn 2 O 3 /C nanocomposite was synthesized from chitosan, a renewable biopolymer, NiO and MnO 2 and pyrolyzed at 500 °C under nitrogen. The morphology of material was characterized with various microscopic analyses. The graphitic carbon showed metal nanoparticles dispersed on the nanocomposite that could be clearly differentiated. X‐ray photoelectron spectroscopy indicated the Mn species reduced from +4 to +3 oxidation state, while Ni species remained as NiO, which was further supported by X‐ray diffraction. The electrochemical behavior of NiO‐Mn 2 O 3 /C toward oxygen reduction reaction (ORR) in alkaline medium was investigated via cyclic voltammetry (CV). CVs revealed a ORR peak at 0.67 V vs . RHE with significantly high current density. Hydrodynamic studies indicated that NiO‐Mn 2 O 3 /C catalyzed ORR via a four‐electron reduction pathway. A high rate constant in the order of magnitude of 10 6 mol −1 s −1 was obtained for ORR. This low‐cost, environmentally friendly and stable ORR catalyst derived from chitosan and doped with metal oxides proved to be a promising electrocatalyst for ORR and could alternatively find its application in alkaline fuel cells (AFCs).