Nitrogen doped graphene supported α-MnO2 nanorods for efficient ORR in a microbial fuel cell

Abstract

Oxygen reduction reaction (ORR) is one of the rate-limiting processes in MFCs. The development of highly active, cost-effective, scalable, and durable catalysts for ORR in MFCs is a challenging task. In this work, we have developed α-MnO₂ nanorods (MN), α-MnO₂ nanorods supported on reduced graphene oxide (MN/rGO), and α-MnO₂ nanorods supported on nitrogen doped reduced graphene oxide (MN/NrGO) through a facile one-step hydrothermal method. The as-prepared electrocatalysts are characterized for morphological and structural evaluation along with electrochemical characterizations. The electrochemical properties of as-prepared catalysts have been investigated through rotating disc electrode (RDE) studies, which confirm that both MN/NrGO and MN/rGO exhibit higher current density, more positive onset potential, and a higher number of electron transfers as compared to both pure rGO and MN individually. The experiments are conducted in a novel MFC having a modular air cathode. Electrochemical performance studies show that the MFCs having a cathode coated with MN/NrGO and MN/rGO electrocatalysts, at a very low loading of 0.5 mg cm⁻², produce maximum power densities of 135.27 mW m⁻² and 85.45 mW m⁻², respectively, which is significantly higher as compared to pure rGO (57.63 mW m⁻²) and MN (45.56 mW m⁻²) electrocatalysts. These results illustrate that MN/NrGO electrocatalysts are potentially efficient and cost effective cathode catalysts for their practical application in MFCs.