Preparation Of Fe-N-C Catalysts And The Application In Cathodic Oxygen Reduction Reaction

The pollution caused by burning conventional fossil energy sources triggers people’concern about environmental degradation,so the utilization and exploitation of clean energy is getting widespread attention.Proton exchange membrane fuel cells（PEMFCs）,featuring high energy conversion efficiency and the product of mostly clean and non-polluting water,is very promising new energy device.However,the low working temperature of PEMFCs and the oxygen reduction reaction（ORR）at the cathode still require a lot of precious metal platinum catalysts,and the limited amount and high cost of platinum reserves significantly hinder the commercialization of fuel cells,in order to overcome this challenge,there is an urgent need to explore more applicable and affordable non-platinum catalysts.Among the non-platinum catalysts,iron-nitrogen co-doped carbon materials with the higher intrinsic catalytic activity and are currently an important research direction and topic.However,the current activity and stability of Fe-N-C catalysts still need to be improved due to the harsh usage conditions of PEMFCs.Metal organic frameworks（MOF）have become ideal precursors for the preparation of highly active Fe-N-C catalysts due to their large specific surface area and convenient adjustable porous structure.In this paper,a series of highly active and stable Fe-N-C catalysts were obtained through the rational design of MOF precursors and the optimization of catalyst preparation process,and the effects of catalyst structure and active sites on the catalytic performance of ORR were investigated in several dimensions,the main contents of this research are as follows:（1）Using ZIF-8 as a carrier for constructing high-efficiency Fe-N-C catalysts and doping iron acetylacetonate in the synthesis of the precursor,further trapping the domain of MOF using graphene oxide material,a series of high-efficiency Fe-N-C catalysts with different components were prepared by a simple high-temperature pyrolysis method,and the efficient iron doping and guest limiting strategy significantly enhanced the oxygen reduction activity of the catalysts in During the oxygen reduction test,the best catalyst Fe-N/GNs reached a half-wave potential of 0.761 V in the acidic test and a more positive half-wave potential of 0.834 V in the alkaline test,with an oxygen reduction activity close to that of commercial platinum carbon,showing preliminary application potential.（2）To address the shortcomings of conventional pyrolytic Fe-N-C catalysts such as insufficient activity and poor pore structure,we proposed a novel dual optimization strategy to construct a large amount of encapsulated iron and intrinsic Fe-N coordination sites in the precursor ZIF-8,followed by the introduction of g-C₃N₄ during the thermal fusion recombination process to promote the conversion of encapsulated iron and intrinsic Fe-N coordination sites in the precursor to Fe-Nx active sites,and prepared The best catalyst Fe-NPC/GNs-1 reached a half-wave potential of 0.771 V in acidic medium and 0.917 V in alkaline medium,which is nearly 30 m V higher than that of commercial platinum carbon,and its potential almost did not decay after 10,000 cycles,showing great potential for applications in proton exchange membrane fuel cells and zinc-air batteries.The potential is almost non-decaying after 10,000 cycles,showing great potential for applications in proton exchange membrane fuel cells and zinc-air batteries.