Preparation And Study Of Orderly Multilevel Pore Structure Fe-N/C Catalyst For Oxygen Reduction

High cost and poor durability are the two bottlenecks of proton exchange membrane fuel cell(PEMFC) which is a kind of clean energy conversion system for its commercial applications, including the high cost of precious metals Pt in cathod catalyst. Development the highly active catalyst in the fuel cell under the oxygen reduction environment has been a key focus in the field of PEMFC.This paper focus on the one step synthesis method, by using urea resin, phenol, and formaldehyde. Based on this template, we join the metal iron in the process of the final heat treatment after two get nitrogen doped carbon carrier iron catalyst for oxygen reduction, and optimize the iron content, the urea content and the secondary pyrolysis temperature. Then testing and characterizing the performance of the catalysts, mainly including electrochemical performance test, TEM, XRD, IR, etc. The results show that the perfotmence of the secondary heat treatment is better than the first heat treatment from the point of the electrochemical properties, and catalytic activity of the catalyst in ammonia atmosphere pyrolysis will have more nitrogen in the mixed catalyst, which is more greater than that from the nitrogen atmosphere pyrolysis. phenolic resin and urea molar mass ratio wae s we will get the best electrochemical catalytic activity of catalysts under with the Secondary heat treatment temperature of 800 ℃, and the iron ion of 0.07. The reduce or increase of the temperature and metallic iron content will lead to reduce the electrochemical properties of the catalyst. It will produce ferroferric oxide and reduce the catalyst performance because the pyrolysis temperature is too high. Urea resin pyrolysis lost with the atmosphere in the process of pyrolysis, but most fragments of the nitrogen, iron and carbon stay, which become the main source of catalyst active sites. The result show that the catalyst has a high degree of ordering pore structure from the transmission electron microscopy(TEM) figure. Good oxygen reduction catalytic activity may also have a close relationship with this special structure. Heat treatment temperature and transition metal iron content and nitrogen content had a greater influence on the catalytic activity of the catalysts, which are the important factors of catalytic active site formation, but the material structure of the active site in the catalyst, its formation mechanism, and the catalytic mechanism needs the further research. The ordered mesoporous catalysts by the experimental synthesis has a better stability than 20wt% Pt/C catalyst. The exchange current density of this ordered mesoporous catalysts was calculated by 1.34×10-9 A/cm2, which is close to the exchange current density of Pt/C catalyst. We also calculated the number of the electron transfer is 3.83, which shows that the O2 in the oxygen reduction reaction mainly generate H2 O by a 4 electronic reaction control process.