Synthesis Of Iron-Based Nitrogen-Doped Carbon Catalyst And Their Oxygen Reduction Reaction Performance

Fuel cells and metal-air batteries have attracted extensive research interest due to their low cost,high specific energy and environmental friendliness.However,limited by the slow oxygen reduction reaction at the cathode,the performance of the batteries cannot be further improved.The current commercial Pt/C catalyst is affected by high cost,poor cycle stability and resistance to methanol toxicity,which hinder its further application in the above battery equipment.Therefore,the development of non-noble metal-based catalysts with low cost,high stability and methanol resistance has become the current research goal.Among them,Fe-based materials have become one of the ideal research objects to replace commercial Pt/C catalysts due to their low cost and high catalytic activity.Currently,transition metal Fe-based materials supported on nitrogen-doped carbon substrates exhibit high ORR activity and stability.However,most studies focus on the effect of atomic structure around Fe sites on the charge arrangement,and ignore the effect of N/C substrate on ORR activity.In this paper,through the design and preparation of Fe-based nitrogen-doped carbon materials,the morphological structure and electrochemical properties are used to find the best preparation process of Fe-based nitrogen-doped carbon materials,and in-depth analysis of the effect of N/C substrate on iron-based active sites the role of points.The main research contents are as follows:（1）Using ZnCo-ZIF as the precursor template,the Fe Co alloy was encapsulated in a nitrogen-rich substrate through the coating of dicyandiamide resin.Then the Fe Co-N/C composite material was prepared by pyrolysis.The Fe Co-N/C catalyst with the best ORR activity has a half-wave potential of 0.82 V and has excellent cycle stability.The effect of nitrogen-doped carbon support has been preliminarily explored.The order of the effect of supporting metal active sites on the substrate on the catalytic activity is:Fe Co alloy>Fe₃C>Co elemental substance.Not only that,the activity of Fe Co alloy is also affected by the morphology and structure of the catalyst.（2）Using a combination of coordination method and template method,a hierarchical porous Fe-N/C catalyst with highly dispersed Fe active sites on a nitrogen-rich carbon substrate was prepared by high-temperature calcination and etching.Fe-N/C material shows good ORR activity(E_1/2=0.835 V)and excellent cycle stability.Through morphological structure characterization and electrochemical testing,it is found that anchoring highly dispersed Fe active sites on a low-activity N/C substrate can greatly improve the ORR catalytic activity of the material.（3）The porous N/C supports were prepared by the one-pot method,and the influence of nitrogen doping on the catalytic activity of the C supports were discussed through the characterization of morphology and electrochemical performance.Furthermore,a secondary pyrolysis process is used to load highly dispersed Fe-N active sites on the N/C supports in situ to prepare porous Fe-N/C catalysts.Among them,the Fe-N/C catalyst prepared on an appropriate amount of N-doped support has the best catalytic activity,with a half-wave potential of 0.856 V.In addition,Fe-N/C also exhibits excellent resistance to methanol toxicity and cycle stability.Through characterization,it is found that when the N/C supports has an appropriate N doping content,it has a higher ability to protect Fe during pyrolysis,and an appropriate amount of N doping can improve the catalytic activity of Fe-N/C materials.The activity is derived from highly dispersed Fe and pyridine-N atoms.This work provides reference for the supports design,synthesis and application of the preparation of Fe-based nitrogen-doped carbon composite materials.