Metal–organic framework derived vanadium oxide supported nanoporous carbon structure as a bifunctional electrocatalyst for potential application in metal air batteries

Abstract

High-efficiency, sustainable, non-precious metal-based electrocatalysts with bifunctional catalytic activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are essential for metal–air batteries. In this research, a bifunctional electrocatalyst is developed by synthesizing a novel nanoporous vanadium oxide/carbon composite (NVC-900) through pyrolysis of a highly efficient vanadium metal–organic framework, MIL-101 (V). The fabrication process was conveniently carried out by pyrolyzing the synthesized MIL-101 (V) at 900 °C, producing vanadium oxide nanoparticles embedded in the extensively distributed pores of the carbon network. The evenly distributed nanopores substantially improve the performance of the efficient electrocatalyst for both the oxygen reduction reaction and oxygen evolution reactions (ORR/OER) by increasing surface area and facilitating access to stable catalytic active sites. The unique structure was characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). For oxygen reduction reaction (ORR), the electrocatalyst established a promising limiting current density (J_L) of 5.2 mA cm⁻² at 1600 rpm at an onset potential of 1.18 V and a half-wave potential of 0.82 V, and for OER, a current density of 10 mA cm⁻² was delivered at a potential of 1.48 V. In comparison to 10% Pt/C, the synthesized bifunctional electrocatalyst being almost equally active towards bifunctional activity, showed much better long-term cyclic stability. The one-step thermal pyrolysis strategy to synthesize the nanoporous functional material and the proposed electrocatalytic material's long-term bifunctional activity and durability make it an ideal fit for next-generation portable green metal–air batteries.