Local Electronic Structure Control Of Monoatomic Dispersion M-NC Catalyst And Fuel Cell Application

The H2-O2 fuel cell which is a technology to efficiently realize the use of clean energy.During operation,the slow oxygen reduction reaction(ORR)that occurs inside the battery seriously hinders the development of hydrogen-oxygen fuel cells and limits their application in the process of industrialization.At present,noble metal catalysts are often used in industry,such as commercial Pt/C,which have high catalytic activity,but their high cost,easy adsorption of phosphoric acid molecules and shortage of resource reserves severely limit the use of noble metal catalysts in low temperature/high temperature fuels.The application in batteries,therefore,the development of transition metal carbon-nitrogen materials has become the focus of current research.More and more studies have found that iron-nitrogen-carbon materials have higher catalytic activity in catalyzing ORR reactions and are the most likely materials to replace precious metal catalysts.As far as the existing Fe-NC catalyst is concerned,there is still room for improvement in its catalytic activity and stability.The commonly used methods of improvement are as follows:(1)Increase the metal load;(2)Increase the specific surface area of the catalyst;(3)Heteroatom doping;(4)Synergistic regulation of bimetallic atoms.Based on this,this topic focuses on the development of transition metal carbon-nitrogen materials,mainly focusing on two aspects:On the one hand,the iron-nitrogen-carbon material is doped with hetero-elements and the heteroatoms are used to change the electron cloud density at the catalytically active site to promote the process of oxygen reduction reaction,thereby promoting the occurrence of the entire ORR reaction.At the same time,through the enrichment of the charge at the active site,the tolerance to phosphoric acid molecules is improved,so that the heteroatom-doped iron-nitrogen-carbon material has a higher catalytic activity in high-temperature fuel cells;on the other hand,in On the basis of the metal monoatomic nitrogen-carbon material,the second metal is doped through the etching and impregnation process.The specific research content is as follows:(1)Using organic small molecule formamide as a carbon source and nitrogen source,through its self-polymerization reaction,the doping of hetero-element phosphorus is realized,and it is used as a multidentate ligand to chelate metal atoms.The most important thing is that,through DFT calculations,it can be known that when phosphoric acid is doped to compete with oxygen for adsorbing active sites,the catalyst’s tolerance to phosphoric acid molecules is enhanced,resulting in excellent high-temperature fuel cell performance.(2)Using formamide as a solvent,using the synthesized transition metal monoatomic nitrogen-doped carbon material as the substrate,etching it by the oxidation of hydrogen peroxide to obtain defect-rich carbon material,and finally through the impregnation method,Load another metal element to prepare a diatomic catalyst after high-temperature carbonization.In addition,the universality of the above method was verified by synthesizing different bimetallic catalysts.This paper is mainly a series of researches carried out around formamide.The purpose is to obtain transition metal nitrogen-carbon materials with high catalytic activity and high stability,and can still maintain good battery performance in low-temperature/high-temperature fuel cells.The potential for large-scale applications.