Construction And Properties Of Oxygen Reduction Catalysts Based On Fe-N₄ Macrocyclic Complexes

With the development of society,the shortage of fossil energy and the increasing environmental pollution,the development of a sustainable and environmentally friendly energy storage and conversion device is an urgent problem in the current energy field.At present,among the energy devices that have been researched and developed,fuel cells and zinc-air batteries are favored by scholars because of their advantages of high energy density,diversified material selection,and low environmental pollution,and are regarded as new choices for future energy devices.At present,Pt-based catalysts are considered to be the best Oxygen reduction reaction（ORR）catalysts.Low reserves,high price and poor stability restrict the large-scale application of fuel cells.Therefore,the development of highly efficient and stable non-precious metal ORR catalysts is of great significance for the development of fuel cells.Alternatives to Pt-based catalyst materials include carbon-based monatomic metal cathode oxygen reduction catalysts,especially carbon-based transition metal catalysts with the catalytic active sites of M-N₄（M=Fe,Co,Ni,Cu）,because of their low cost,they can be mass-produced and thus attract more attention.M-N₄sites are often generated by high-temperature heat treatment of transition metals bonded to carbon.However,the carbon-based material structure of the high temperature treated material M-N₄is more complex.Metal phthalocyanine（MPcs）and its derivatives are considered to be one of the most promising catalyst materials due to their high ORR catalytic activity,unique structure,modified ligand structure and optional central atoms.However,conjugations ofπ-πbetween macrocyclic molecules of MPcs usually produce aggregates that limit exposure to active sites,and such complex molecules have poor electrical conductivity.Therefore,MPcs are evenly loaded on the carbon material carrier to expose more M-N₄active sites accessible to O₂.In the second chapter of this paper,porous carbon material Z67C is prepared by preparing ZIF-67 as the precursor and through pyrolysis.Through environmentally friendly non-pyrolysis process,A hierarchical porous carbon material anchored to Fe-N₄（Fe Pc@Z67C-1-2）was prepared by loading M-N₄macrocyclic complex iron Phthalite（Fe Pc）on Z67C material.The results of electrocatalytic tests show that Fe Pc@Z67C-1-2 catalyst has good ORR activity,stability and anti-methanol toxicity under alkaline conditions.Compared with the commercial 20%Pt/C catalyst,the half-wave potential(E_1/2=0.88V)of Fe Pc@Z67C-1-2 catalyst shifted by 30m V.At the same time,the current density value of Fe Pc@Z67C catalyst is better than that of commercial Pt/C catalyst.In terms of stability,after 5000 cycles in alkaline electrolyte solution,Fe Pc@Z67C catalyst still maintains good catalytic activity(E_1/2negative shift 9m V),which is better than commercial 20 wt%Pt/C（negative shift about 14m V）.Fe Pc@Z67C catalyst as the cathode,zinc plate as the anode to assemble the zinc-air battery,the battery performance is good.In the third chapter of this paper,the waste of rose residue after the extraction of rose essential oil from the landmark specialty"Ku Shui Rose"in Yongdeng County of Lanzhou City is selected as carbon precursor of biomass.By drying and crushing rose residue and using potassium ferrate（K₂Fe O₄）as activator,the graded porous carbon material（RPC）with large specific surface area was synthesized.A hierarchical porous carbon material anchored to Fe-N₄has been prepared by loading the M-N₄macrocyclic complex iron Phthalate（Fe Pc）onto RPC materials using an environmentally friendly non-pyrolytic process（Fe Pc@RPC-1-2）.The results of electrocatalytic tests show that Fe Pc@RPC-1-2 catalyst has good ORR activity,stability and anti-methanol toxicity under alkaline conditions.Compared with the commercial 20%Pt/C catalyst,the half wave potential(E_1/2=0.91V)of Fe Pc@RPC-1-2 catalyst shifted 60m V.At the same time,the current density value is better than that of commercial Pt/C catalyst.In terms of stability,Fe Pc@RPC-1-2 catalyst still maintains good catalytic activity(E_1/2negative shift about 20m V)and commercial 20%Pt/C（negative shift about 14m V）after 5000 cycles in alkaline electrolyte solution.The zinc-air battery was assembled with Fe Pc@RPC-1-2 catalyst as cathode and zinc plate as anode.Its open-circuit voltage is 1.437V,and it has a high specific capacity of 677.2m Ah·g^-1and a power density of 78.0m W·cm^-2.The long-term cycle test of 143 hours further shows that its stability is good.In this paper,MOFs and biomass were used as precursors to design and prepare non-noble metal ORR catalysts,and the physical and electrochemical characterization of the materials were carried out.It has good oxygen reduction performance and zinc air battery performance.A new perspective is developed for the design and development of metal-air batteries and other energy storage devices.