Transition Metal Phosphide Embedded In N,P Co-doped Porous Carbon Nanosheets As High-efficiency Oxygen Reduction Electrocatalyst For Zinc-air Battery

With the depletion of fossil fuels,people are paying more and more attention to the increasingly serious environmental problems.Among the many new energy storage and conversion systems,zinc-air batteries（ZABs）have the advantages of high energy density and green environmental protection,have received widespread attention.The core of its work is based on the oxygen reduction reaction（ORR）,which has the problem of kinetic slowness.In order to improve the performance of the battery,it is necessary to add a catalyst to increase the ORR reaction rate.Although platinum-based electrocatalysts have excellent ORR catalytic activity,their high cost and poor stability greatly increase the cost of batteries and hinder the commercialization of ZABs.Therefore,for the sake of solve this key problem,there is an urgent need to develop inexpensive and efficient non-noble metal-based ORR catalysts to replace platinum-based catalysts.There are many types of non-noble metal-based ORR catalysts.Among them,N,P co-doped carbon materials coated with transition metal phosphides have sufficient development potential.This is because the N,P co-doped carbon skeleton has many surface defects,which can be a good ORR catalytic active site,and the inner coated transition metal phosphide itself has good electrical conductivity,which is conducive to the electron transfer in the reaction process,and further improve the ORR reaction kinetics.Moreover,the transition metal phosphide and the N,P co-doped carbon skeleton have a strong interaction,which is beneficial to keep the structure of the catalyst stable during the electrocatalytic reaction.Based on the above discussion,this thesis conducts the following specific research contents:1.Through electrostatic interaction,melamine,phytic acid and graphene oxide are self-assembled to form a precursor compound,and Fe³⁺is directly introduced into the precursor by using the strong interaction between the phosphorus-containing functional group and the metal ion.After the precursor is processed by high-temperature pyrolysis,a nitrogen-phosphorus co-doped carbon nanosheet material（2D-FeP@FeNC-900）coated with iron phosphide nanoparticles is generated in situ.There is a synergistic effect between iron phosphide nanoparticles and nitrogen-phosphorus co-doped carbon nanosheet framework,which improves the intrinsic activity of ORR.The liquid rechargeable ZABs with 2D-FeP@FeNC-900 as the catalyst have an ultra-high peak power density of 260 mW cm^-2.2.Using graphene oxide as a substrate,the polymerization reaction of 2,6-diaminopyridine and phytic acid is initiated by ammonium persulfate（APS）to generate polymer precursors in situ on the graphene oxide,the phosphorus-containing functional groups and metal The strong interaction of ions introduces Fe³⁺directly into the precursor.After the precursor undergoes high-temperature pyrolysis and pickling treatment,a nitrogen-phosphorus co-doped carbon material containing iron single atoms（Fe-N_X）coated with iron phosphide nanoparticles is produced.N,P co-doped carbon skeleton containing Fe-N_X and iron phosphide nanoparticles have a better synergistic effect,and this material should have higher ORR catalytic activity.