MOFs-derived Transition Metal-N-carbon Cathode Catalysts And Their Electrochemical Performances

With the development of the economy,the rapid environmental deterioration and the energy crisis have an urgent demand for the development of energy storage and conversion.Asnew-style energy devices,microbial fuel cells?MFCs?are differentfrom traditional fuel cells.In the MFCs,the microorganisms can transform organic waste directly into electricity.Recently,MFCs have developed rapidly owing to their environmentally friendlyadvantages.However,there are still several major technical issues that still limit their further development,such as the low power density and high-cost catalysts.In particular,the high cost andvulnerable stability of Platinum-based cathode materials hinder the practical application of microbial fuel cells.Therefore,it still remains challenging to develop stable and efficient non-precious cathode catalysts with high ORR performance.In this paper,metal-organic frameworks?MOFs?were successfully synthesized as precursor.After the pyrolysis process,the composite consisting of metal nanoparticles encapsulated in N-doped carbon was successfully obtained.In order to demonstrate the feasibility of cathodic catalyst,the electrochemical characterization and MFCs performance were under investigated.Concrete research contents are as follows:?1?ZIF-67 precursor were successfully synthesized through 2-methylimidazole and cobalt nitrate.After carbonization,a novel Co-N-C eletrocatalyst derived from ZIF-67was obtained.The Co-N-C-2 exhibited a superior ORR performance and high power density when tested as cathode catalyst in single-chamber MFCs.Due to the structure of metal-nitrogen-carbon,the Co-N-C-2 achieved the maximum power of399.7±10 mW m^-2.?2?A novel N-C@CoFe cathode electrocatalyst derived from bimetal Fe/Co-ZIF was obtained.The process of prepared bimetal CoFe decoratednitrogen-dopedhollow carbon was used silicon spheres as template,which was effectively hinder the formation of large ionic groups.In addition,after etching the silicon spheres in alkaline medium,the honeycomb-like structure catalysts were obtained.Benefit to the unique structure,the active sites and surface areaof the catalysts were enhanced.?3?Ni₃Fe-N-C-800 composites were successfully synthesized through Fe/Ni-MOFs.Due to the synergistic effect between Ni₃Fe particles and N-doped carbon,the as-prepared Ni₃Fe-N-C-800 exhibit high activity and stability.The as-prepared materials exhibit superior ORR performance whichis comparable to Pt/C.In Zinc-air battery,the maximum output power can reach to 120.3 mW cm^-2,which mainly attributed to the unique structure.