Preparation Of Fe/Co-NC Catalyst And Study Of Its Catalytic Properties

Proton exchange membrane fuel cells(PEMFCs)have been considered the ideal clean energy conversion device due to the advantages of fast start-up,no pollution.Nevertheless,by the two major constraints,PEMFCs technology is still in the primary stage of development.First,the cost of expensive materials and assembly process,such as the use of Pt catalyst and proton exchange membrane,resulting in the overall cost of PEMFCs is 10?20 times the traditional heat engine.Second,low activity,poor stability and the the Pt-based electrode also suffers from low tolerance to CO“poisoning”.Therefore,development of Pt-free catalysts instead of Pt-based catalysts for great importance to accelerate the large-scale use of PEMFCs.In recent years,Pt-free catalysts has been attracting People's attention because of its high activity and stability.The transition metal-nitrogen-carbon catalyst(M-N-C)(M = Fe,Co,Ni,Cu,Cr,etc.)is considered to be one of the most promising cathodic catalysts due to its rich sources of raw materials,low cost and good catalytic activity and stability.During the process of the aniline polymerization,Iron salt and bivalent Cobalt salt with different anionic groups were added into the solution and then different polyaniline cobalt(PANI-M)coordination polymer were obtained.Finally Fe-N-C or Co-N-C carbon-based catalysts were prepared through pyrolysis of PANI-M coordination polymer.The morphology,structure,chemical composition and Chemical valence of the M-N-C catalysts were characterized by transmission electron microscopy(TEM),scanning electron microscopy(SEM),X-ray spectroscopy(XRD),X-ray photoelectron spectroscopy(XPS)and Raman spectra(Raman)in order to study the Fe-N-C catalyst and Co-N-C catalysts.The electrocatalytic activity of M-N-C catalysts were tested by electrochemical method.The main findings are as follows:(1)The milling time will have a great influence on the degree of graphitization of Fe-N-C catalyst,the element content of the surface and the chemical state of the element.With the increase of milling time,the activity of Fe-N-C catalyst increases,The Fe-N-C catalyst has the best catalytic activity when it increases to 90min,and then increases the activity of milling time.(2)The Cobalt salt anionic groups had little impact on the morphology of Co-N-C catalysts,but had a great influence on the content and surface chemistry of Co-N-C catalysts,carbon structure,degree of graphitization and the valence of Co.The Cobalt salt anionic groups could affected the electrocatalytic activity of Co-N-C catalysts.The catalytic activities decreases as(C2H3O2)22-->Cl22->(NO3)22->SO42->C2O42-.The Co-N-C catalysts prepared by(C2H3O2)22-and C122-anions had higher ORR activity,possibly due to the higher content of graphite nitrogen and pyridine nitrogen.