Preparation And Oxygen Reduction Properties Of Transition Metal-doped Mesoporous Nitrocarbon Materials

Fossil energy is facing the increasingly serious energy crisis and environmental crisis because of its non-renewable and burning pollution in recent years.Transformation of the mode of energy development,therefore,the use of new renewable green energy has become the first key task.Fuel cell and zinc-air battery because of the advantages of high energy density and green environmental protection,energy field has wide application potential in the future.Problems existing in the cathodic oxygen reduction reaction kinetics is slow,seriously affect the energy conversion efficiency of the battery,need to develop efficient electric catalytic catalyst for oxygen reduction reaction.At present,the commercial oxygen reduction reaction platinum catalyst is expensive and poor stability,how to prepare non-noble metal catalysts to replace noble metal catalyst,has become a hot spot of research.As a kind of universal substrate material,carbon-based materials have been widely used in various fields of catalysis and energy storage,but their performance needs to be further optimized by composite materials.Spray drying method of synthesis nanometer materials has the advantages of fast and efficient and low cost has been realized in industrial scale application.In this thesis,the spray drying method of synthetic nitrogen doped mesoporous carbon,and then to transition metal modification,synthesis of different carbon composite catalyst,used in the fuel cell and zinc air battery cathode reaction,and achieved excellent performance The main research content is as follows:(1)A nitrogen-doped mesoporous carbon catalyst containing trace of Fe(FeNC)was synthesized for efficient catalytic oxygen reduction reactions.The nitrogen-doped porous carbon spheres prepared by spray drying method have high specific surface area and excellent electrical conductivity,which can effectively promote the electron transfer in the reaction process and improve the kinetic performance of electrochemical reaction.The Fe doped carbon material has excellent oxygen reduction reactivity,similar to the activity level of commercial Pt/C,and has the advantages of toxicity resistance and strong stability that Pt/C does not have.(2)A composite catalyst(Co₂P/Co-NC)consist of Co₂P nanoparticles and Co-NC was synthesized.By using Vitamin B12 as cobalt source and phosphorus source,nitrogen-doped mesoporous carbon spheres as carbon substrate material,the Co₂P/Co-NC was prepared by evaporation and calcination at high temperature.Experimental data and theoretical calculations show that the presence of Co₂P nanoparticles can be used as a cocatalyst to adjust the electronic structure of Co-NC metal center.Co₂P/Co-NC has excellent oxygen reduction reaction performance in alkaline conditions,and the half-wave potential reaches 0.87 V,comparable to commercial Pt/C.The material was tested as a cathode catalyst for zinc-air batteries,and it was found that the material also has potential in practical applications.(3)Fe-NPC catalyst was synthesized by in-situ one-step method.In order to further improve the dispersivity of the metal structure of carbon nitrogen and simplify the synthesis methods,design a kind of in-situ one-step synthesis of a new method of Fe-NPC catalyst.The method is simple in operation and can be achieved in situ load metal,can effectively avoid the metal in the process of calcination gathered themselves together,and have high specific surface area of catalyst,is advantageous to the oxygen reduction reaction.In alkaline conditions,its performance is similar to that of commercial Pt/C,and its stability and methanol toxicity resistance are better than that of Pt/C.This method is more suitable for industrial production,with higher yield and convenient operation.