Study of high temperature pyrolysis effects on the performance of co-doped metal-organic framework with nitrogen-doped reduced graphene oxide for the oxygen reduction reaction

Abstract

In this study, the electrochemical performance of nitrogen-doped reduced graphene oxide (N-rGO) combined with cobalt-doped MOF catalyst is investigated after annealing at different temperatures for application with proton-exchange membrane fuel cells (PEMFCs). The material was characterized using FTIR and Raman spectroscopy, XRD, SEM, XPS, and BET analysis to understand variations in its physical and chemical properties. Our results reveal the formation of the (100) cobalt-doped ZIF-8 phase, with a distinct crystalline-to-amorphous transition upon increasing the pyrolysis temperature to 900 °C, resulting in increased porosity and a fluffy microstructure. Linear sweep voltammetry studies reveal that incorporating the transition metal onto reduced graphene oxide (rGO) significantly enhances electrochemical performance compared to non-transition metal carbon-based catalysts. The optimized material composition exhibited comparable oxygen reduction reaction (ORR) performance to a commercially available 40 wt% Pt/C catalyst, achieving a potential of 0.495 V vs. RHE at -1 mA⋅cm^− 2 and similar cathodic currents. This improvement is attributed to the porous metal-organic framework (MOF) structure, which exposes numerous active cobalt and nitrogen sites on the surface, along with rGO, which enhances conductivity. dy underscores the role of nitrogen doping and pyrolysis in enhancing ORR activity, providing deeper insights into these electrocatalytic systems.