Preparation Of Non-noble Metal Doped Carbon-Based Catalysts And Their Catalytic Performance For Oxygen Reduction

Due to the increasing consumption of traditional fossil fuels（coal,oil,natural gas,etc.）and environmental pollution（smog,greenhouse effect,etc.）,people’s daily lives are seriously affected,and researchers have to find alternatives to traditional fossil fuels.People’s demand for sustainable energy storage and conversion devices is also increasing.Fuel cells are gradually entering the public’s field of vision due to their high conversion efficiency and environmental friendliness.The slow reaction rate of cathode oxygen reduction and the high cost of the Pt/C catalyst used are the main reasons that currently affect the commercialization of fuel cells.Therefore,the development of non-precious metal catalysts with low price and excellent activity has gradually become a current research hotspot.There are many types of non-precious metal catalysts.Among them,transition metal and heteroatom co-doped catalysts are the most widely studied.The goal of this paper is to study the active center of the catalysts,and introduce several different preparation methods to synthesize a series of different transition metals and heteroatoms.The morphology,structure,composition and oxygen reduction catalytic activity of the atom-doped carbon-based catalyst were characterized in detail.The main contents and results are as follows:1.Using Zn-based ZIFs as the metal template and Fe as the metal source,a new type of nitrogen-doped carbon nanoflower（Fe₃C@NC）with in-situ generated Fe₃C embedded carbon nanotubes were prepared by a one-step pyrolysis method.The effects of different Fe content and pyrolysis temperature on the catalyst activity were studied.The amount of Fe doped is the most critical factor for the formation of Fe₃C active sites.The synergistic effect of Fe₃C active sites and high content of pyridine N improved the catalytic activity of oxygen reduction reaction（ORR）.Fe₃C@NC-60-800 catalyst has high initial potential（Eonest,0.987 V）and half-wave potential(E_1/2,0.863 V),indicating that it has excellent ORR catalytic activity and excellent resistance to methanol poisoning Ability and stability.The proposed synthesis strategy provides new methods and ideas for the design and construction of metal-organic framework-derived nanomaterials.2.A new type of FeP nanoparticles which self-intercalated P and N co-doped hierarchical porous carbon with multiple active sites（FeP@NPC）were prepared by a one-step salt template-assisted high-temperature pyrolysis strategy.NaCl crystals provided a template for the carbon precursor（glycine）to generate rich and orderly porous carbon,while Fe（NO₃）3.9H₂O and（NH₄）2HPO₄ were used as iron,nitrogen and phosphorus precursors to prepare FeP,and further In-situ P and N were co-doped into the porous carbon framework.Due to the unique hierarchical structure and synergy of FeP nanoparticles and P,N-doped carbon,FeP@NPC shows excellent ORR catalytic activity.FeP@NPC-90-900 has high starting potential（Eonest,0.957 V）and half-wave potential(E_1/2,0.863 V),good stability and methanol tolerance,which are better than expensive commercial products Pt/C catalyst.The method is simple and scalable,and opens up a way for the rational design of metal phosphides as non-noble metal catalysts for ORR.3.Using ZIF-67 as the organometallic template and FeCl3 as the pore former and metal source,N-doped dodecahedral carbon modified with FeCo bimetallic nanoparticles with controllable microstructure and catalytic efficiency were prepared by the secondary carbonization method.catalyst.By adjusting the amount of Fe doping,the optimal catalyst FeCo-NC-60-900 has a hierarchical porous structure,large specific surface area,and abundant active centers（pyridine nitrogen,graphite nitrogen and Fe-Nx）.The catalyst has the best catalytic effect in 0.1 M KOH,and its half-wave potential is as high as 0.874 V,which exceeds the commercial Pt/C by about 20 mV.This synthesis method takes into account the ORR catalytic activity and improves the stability of the catalyst.It provides a new strategy for realizing bimetal doping and increasing the active sites of M-Nx（M=Fe,Co）.