Preparation,Characterization And Application Of Nitrogen Doped Carbon-Based Non-Noble Metal Catalysts In Oxygen Reduction

In this work,we successfully synthesized N-doped mesoporous carbon spheres?NMCS?through electrospun combining hard templates method.Meanwhile,the carbon sphere showed excellent electrocatalytic activity towards the ORR performance in alkaline conditions.Subsequently,we introduced iron into nitrogen-doped mesoporous carbon spheres and prepared a Fe/N co-doped carbon sphere?Fe-N/MCS?catalyst,and optimized the preparation conditions of Fe-N/MCS.The detailed works of this paper are as follows:1)NMCS were synthesized through electrospun combining hard templates method.The results show that the catalyst prepared at 800?C calcination temperature and 30%template ratio has the best morphology.Although the onset potential is 51 mV more negative than Pt/C catalyst,the maximum limiting current density of the catalyst(6.19 mA cm^-2)at 1600 rpm is higher than that of commercial Pt/C(6 mA cm^-2).2)Iron-nitrogen co-doped mesoporous carbon spheres?Fe-N/MCS?catalysts were prepared from four different iron sources?ferrous nitrate,ferric chloride hexahydrate,ferrocene and iron triacetylacetonate?.The morphology and oxygen reduction activity of the four samples were studied.The highest iron content is 0.13%when the iron source is ferrous nitrate hydrate?Fe-N/MCS-181?.In addition to excellent reduction activity,the catalyst exhibited better durability commercial Pt/C.Compared with loss 15.8%of the initial current density,the prepared catalyst displays a less than 13.6%decline after continuous operation for10000 s.3)The effect of different iron content on the morphology and performance of the catalyst was explored through changing the amount of iron precursor to identity the structure-activity relationship between its structure and oxygen reduction activity.We founded that it is not that the higher of the iron content,the better the catalytic performance.When the iron content is0.18%,the half-wave potential and the onset potential of the catalyst are-0.008 V and-0.136V,respectively.Compared with commercial Pt/C,the catalyst has better ORR catalytic performance.The current retention contains 90.6%after continuous operation for 10000 s,which is more durable than commercial Pt/C.This may be attributed to the abundant active nitrogen?pyridine nitrogen and pyrrole nitrogen?in Fe-N/MCS-1.5,which is easy to promote the formation of Fe²⁺-N₄ active structure with Fe²⁺.