Robust bimetallic metal-organic framework cathode catalyst to boost oxygen reduction reaction in microbial fuel cell

Metal-organic frameworks (MOFs) have emerged as versatile materials for widespread energy and environmental applications due to their intrinsic physical and chemical properties. To this extent, this research is focused on the synthesis of novel amine-functionalized single (Zr) and bimetallic (Zr, Ni) MOF viz. NH2-UiO-66(Zr) and NH2-UiO-66(Zr/Ni), followed by their testing as cathode catalysts to improve oxygen reduction reaction (ORR) in a microbial fuel cell (MFC) for bioenergy recovery from organic wastes. The physical and chemical characterization techniques depicted the successful synthesis of octahedral-shaped MOF nanoparticles with similar structural integrity despite the incorporation of the secondary metal ion. However, electrochemical analyses demonstrated NH2-UiO-66(Zr/Ni) as a better catalyst, achieving a high ORR peak current, low charge transfer resistance, and high diffusion coefficient as compared to both NH2-UiO-66(Zr) and 10% Pt-C catalyzed cathodes. MFC performance evaluation further confirmed the high catalytic activity of NH2-UiO-66(Zr/Ni), allowing to recover a power density (PD) of 0.8 W/m2 at a coulombic efficiency (CE) of 75.4%, outperforming the MFC using 10 % Pt-C catalysed cathode. This study suggests that the NH2-UiO-66(Zr/Ni) can be used as an efficient ORR catalyst for application in large-scale MFCs.