Synthesis and characterization of Zn (zinc), Co (cobalt), Fe (iron) containing metal organic frameworks (MOFs) for microbial fuel cells (MFCs)

Metal organic Frameworks (MOFs) with their unique characteristics such as high surface area, variable functionalities and structural diversity, stability, and porous structure can be used as Microbial Fuel Cell (MFC) cathode catalysts. In this study, MOFs are synthesized from metal salts of zinc (Zn), cobalt (Co) and iron (Fe) and organic linkers as fumaric acid, terephthalic acid, 2-aminoterephthalic acid and 2-methlyimidazole via room temperature and sonochemical synthesis methods which are easy and energy-efficient. Effect of metal doping, reactant molar ratios and concentrations and metal ion precursors on synthesis of MOFs were investigated and formed frameworks are characterized by Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis and X-Ray Diffraction Analysis. Obtained MOFs' applicability as Microbial Fuel Cell (MFC) cathode catalysts are studied by preparing slurries with carbon black (CB) and polyvinyl alcohol (PVA) as binder, coating them on stainless-steel mesh (SSM) current collectors for the first time. Electrochemical characterization of coated SSMs were performed via Chronopotentiometry and Cyclic Voltammetry (CV) and morphology of the coatings were established via SEM. SSM coated with 80% ZIF-L/10% CB/10% PVA slurry demonstrated the best oxygen reduction reaction (ORR) performance via CV. SSMs with ZIF 8/CB/PVA, ZIF-L/CB/PVA, Zn-doped ZIF67/CB/PVA, and MIL-88A/CB/PVA composites that had demonstrated catalytic activity towards ORR utilized in MFCs for further performance analysis by Open Circuit Voltage (OCV), Linear Sweep Voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS) in a two-chamber MFC inoculated with E.Coli K-12. Among the MFCs with novel cathodes, MFC with SSM cathode containing 80% ZIF-L/10% CB/10% PVA coating demonstrated the lowest charge transfer resistance and highest current density.