Preparation And Electrochemical Performance Of Carbon Modified Iron-Based Catalyst For Oxygen Reduction Reaction

Proton exchange membrane fuel cell(PEMFCs)is widely regarded as the best energy conversion technology,mainly because it is not limited by the Carnot cycle,high conversion efficiency,large operating temperature range,higher the power and specific energy,low noise,wide distributed raw materials,safe and sustainable energies,and so on.PEMFCs has important application prospects in many fields,such as electric cars,airplane and submarine.Currently,Pt/C catalyst has the highest ORR activity compared with others catalysts.However,there are still many problems exist.For example,high cost,substrate corrosion catalyst,dissolving of the Pt nanoparticles,poor stability,and fuels can react with catalyst causing catalyst poisoning phenomenon,and significant reduction in the activity of the catalyst.These factors will hinder the large scale commercial application.Therefore,developing inexpensive,environmentally friendly,high efficient catalytic activity of the electrocatalyst has become the focus of improving the performance of PEMFCs.In this thesis,three efficient cathode for electrocatalysts were synthesized by simple method.And their morphological and electrochemical properties were characterized.The main research contants are as follows:(1)Fe3C/NGS catalyst with sandwich structure was prepared by high temperature calcination method using ferric chloride as iron source,melamine as carbon source and graphene oxide as substrate.The characterization of XRD,Raman,SEM,TEM shows that Fe3 C nanocomposites are uniformly dispersed on the thin layers of nitrogen-doped graphene(NGs).And the effect of GO loading on the oxygen reduction activity(ORR)of the prepared catalyst in alkaline medium were also discussed.The experimental results show the prepared catalyst has the highest oxygen reduction activity and exhibits better resistance to methanol and better cycle stability when the loading of GO is 80 mg.The excellent performance of the catalyst could be mainly ascribed to the higher nitrogen content,the abundant Fe-Nx/C-Nx active site,the larger specific surface area and the rich pore structure.(2)The hollow chain like FN-B-800 composites were prepared by by adding 0.02 g ofPVP at a concentration of 4 mmol and a calcination temperature of 800 ° C.And a series of factors such as calcination temperature and precursor concentration were investigated.The experimental results show that the composite catalyst with higher oxygen reduction reaction(ORR)activity and oxygen evolution reaction(OER)activity.It is believed that the PVP can made Fe3 C nanoparticles uniformly distribute in hollow nitrogen-doped carbon nanotubes(n CNTs),thus effectively preventing the aggregation or of Fe3 C.(3)The honeycomb Fe3@NGC catalyst was prepared by high temperature calcination method using glucose as carbon source,urea as nitrogen source and ferric chloride as iron source.XRD,SEM and TEM characterization showed that Fe3 C nanocrystals were evenly distributed on nitrogen-doped graphitized carbon.And the electrochemical properties of the composites were tested too.Compared with Fe3C@GC and NGC,Fe3C@NGC catalysts exhibit excellent electrocatalytic activity,good cycling stability and better methanol tolerance.The good performance of the Fe3C@NGC catalyst are due to greater specific surface area,more reactive sites and more unhindered ion transport channels.