Study On Novel Non-noble Metal Electrocatalysts For Oxygen Reduction Reaction

Proton exchange membrane fuel cell(PEMFC),as a new kind of energy which benefite environmental protection and sustainable development of economy and society,have been researched in the past few decades.As the core component of PEMFC,the cathodic catalysts for oxygen reduction reaction have many problems that hinder their commercial application.The commercial E-TEK Pt/C catalyst has some shortcoming including high cost and poor methanol resistance.These problems make the cathode catalysts have a solw kinetic process and unable to work steadily in the actual application.In this thsis,the preparation of non-noble metal catayst with high catalytic activity is our main task.Metal-organic frameworks(MOFs)material were used as the precursor and template to synthesize three kinds of composited catalysts including nitrogen doped carbon coated Co3O4 cube with Co3[Co(CN)6]2(Co-CO PBA)as precursor.Nitrogen doped carbon coated MnO rod with ?-MnO2 rod as substrate material.And Fe and S co-modified porous N-doped carbon materials with ZIF-8 as the carbon source and nitrogen source.A variety of characterization methods were used to analyze the catalyst's structure,morphology and electrocatalytic activity of oxygen reduction in alkaline media.The detailed work of this thesis is as follows:(1)Aniline was polymerized on the surface of Co-Co PBA to form poly aniline(PANI),and Co/N-C was prepared by pyrolysing Co-Co PBA/PANI under nitrogen protection.And then,Co/Co3O4/N-C was prepared by slow oxidation of Co/N-C in air atmosphere.The structure and size of Co/Co3O4/N-C is characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),Raman spectroscopy,X ray diffraction(XRD),BET.Cyclic voltammetry(CV),Linear sweep voltammtry(LSV)and chronoamperometry(i-t)were used to study the oxygen reduction properties of Co/Co3O4/N-C and the methanol resistance and long-term stability of the catalyst in alkaline medium.The results show that the electrocatalytic performance of Co/Co3O4/N-C is comparable to that of commercial E-TEK Pt/C,but the stability and methanol resistance are better than that of E-TEK Pt/C.(2)?-MnO2 nanorods were used as the substrate material and ZIF-8 was grown on the rods uniformly.Yolk-shell nanorods comprising of nitrogen-doped carbon(N-C)coating on manganese monoxide(MnO)are manufactured via one-step carbonization of a-MnO2/ZIF-8 precursors.The structure and size of MnO/N-C is characterized by SEM,TEM,Raman,XRD.CV,LSV and i-t were used to study the oxygen reduction properties of MnO/N-C in alkaline medium and the methanol resistance and long-term stability of the catalyst.The results show that the onset potential of MnO/N-C is negative than commercial E-TEK Pt/C,but the half-wave potential is more positive compared to that of E-TEK Pt/C.MnO/N-C catalyst has excellent catalytic properties for oxygen reduction and long-term stability.(3)Iron and sulful co-modified nitrogen-doped mesoporous carbon materials(Fe,S,N-C)were prepared by high temperature carbonization of metal organic framework(ZIF-8),and further treatment with ferric rhodanate.The structure and size of Fe,S,N-C is characterized by SEM,TEM,Raman,XRD,BET.At the same time,the electrochemical performances of Fe,S,N-C towards oxygen reduction were tested.Compared with N-C material without Fe and S modification.The half wave potential of Fe modified material was obvious positive.The onset potential of the catalyst material modified by S was positive shift which means S plays a more significant role for improve catalytic properties.The co-modified Fe,S,N-C show the best performance.And after i-t test,Fe,S,N-C has excellent properties of oxygen reduction and long-term stability,far better than that of commercial Pt/C.