Theoretical Study On The Effect Of Electronic Structure Modulation On The Properties Of FeN_x-Gra Oxygen Reduction Electrocatalysts

Proton Exchange Membrane Fuel Cell（PEMFC）,as a kind of power generation device,which generates water through the reaction of hydrogen and oxygen,and converts chemical energy into electrical energy efficiently,has attracted the attention of researchers.However,the cathodic oxygen reduction reaction is very slow,and it is necessary to use catalyst to react efficiently.So far,the platinum-based catalyst is the most widely used one,but it is very expensive,so it can’t be used commercially on a large scale.Therefore,non-noble metal catalysts have become the mainstream research hotspot,among which Fe atoms and N atoms co-doped graphene are the most widely used.In this paper,the first-principles density functional comparison of two catalysts for Oxygen Reduction Reaction（ORR）of proton exchange membrane fuel cells,namely（Graphene,Gra）co-doped by one Fe atom with four N atoms（Fe N₄）and three N atoms（Fe N₃）,was made.The equilibrium configuration,active sites,Density of States（DOS）and charge distribution of Fe N_x-Gra（Fe atom and N atom co-doped Graphene）cathode oxygen reduction catalyst were systematically studied from the point of view that the number of electrons around the metal Fe atom may affect the properties of the catalyst,and the results were deeply discussed and compared.Their properties are different,and the main conclusions are as follows:（1）The two catalysts have the same bonding state between the atoms before and after the adsorption of O₂molecules.Both catalysts have metallic properties and are more prone to electron transfer.However,after the catalyst adsorbs the O₂ molecules,the Fe-O bond and the Fe-N bond produced in the Fe N₃-Gra catalyst are more stable than those produced in the Fe N₄-Gra catalyst.（2）In the two O atoms after the O₂ adsorption of the two catalysts,the O atoms far away from the Fe atoms have the adsorption priority.（3）From the perspective of charge distribution,the two oxygen atoms after the catalyst Fe N₃-Gra are significantly more charged than the Fe N₄-Gra catalyst,indicating that the former shows a more active electron transfer state compared with one less N atom.（4）From the perspective of DOS and charge distribution and change,the active site of both catalysts is the Fe N_xsite.From the electron modulation perspective alone,the Fe N₃-Gra catalyst performs better than the Fe N₄-Gra catalyst.These theoretical calculations provide theoretical guidance and basis for the study of catalyst properties,and also provide some directions for the simulation of catalyst calculation.