Effect Of Modified Carbon Materials On Oxygen Reduction Activity And Stability Of Platinum-based Catalysts

With the development of economy,the exploition and large-scale use of fossil energy have brought serious environmental pollution and so on.Proton exchange membrane fuel cell(PEMFC)attracted great attention due to its advantages such as cleanliness,high efficiency,easy operation,low working temperature and fast start-up.However,its high cost and durability hinder the industrialization of PEMFC.Among them,the platinum-based catalyst used in the cathode is the key factor of the PEMFC cost.Therefore,the investigation of catalyst with low platinum content,high activity,high stability and low cost became hot research field in PEMFC.In this dissertation,carbon supported platinum catalysts were prepared by ethylene glycol reduction method.The effects of FeN co-doped carbon support(active carbon supports and graphene)on the activity and stability of carbon-supported platinum catalyst for oxygen reduction of(ORR)were investigated.The ORR activity and stability of the catalyst were measured by electrochemical characterization.The structure and physical characteristics of catalysts and their supports were studied by an array of techniques such as Brunauer-Emmet-Teller(BET)surface area and pore size distribution measurements,transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and etc.The relationship between the catalytic activity and stability of the catalyst and the structure of the catalyst was investigated.The main results are as follows:1.The activity and stability of platinum-based catalysts,using BP,EC600 JD,FeN co-doped BP and EC600 JD as carbon supported,were studied by electrochemical characterizations.The Pt/Fe(N)BP-10 min showed better ORR activity and stability.2.Using FeN co-doped carbon materials as carbon supports for Pt-based catalysts,the effects of temperature and time of pyrolysis under ammonia on catalysts' activities and stabilities were studied by electrochemical characterizations.The Pt/Fe(N)BP-10 min catalyst using Fe(N)BP obtained under the conditions of 900? and 10 minutes had best ORR activity and stability.Pt/Fe(N)BP-10 min showed much better stability than commercial Pt/C catalyst,with the-10 mV of potential shift and 1.8 % of electrochemical surface area(ECSA)loss.3.The graphene prepared by the modified Hummers method showed better performance.FeN co-doped graphene achieved much better performance than graphene.The Pt catalyst prepared by ethylene glycol reduction method using modified graphene as carbon showed best ORR activities.4.The platinum-based catalysts show much improvement in ORR activities using FeN co-doped carbon materials as carbon support.Combined the results obtained from ADT,BET,TEM,XPS,etc,the doping of FeN on carbon materials modified their physical characteristics such as surface area,defects,types of elements and functional group on surface,etc.The dispersion and size of platinum particles,the interaction between platinum particles and carbon support were improved due to the modification of carbon supports.Most of surface nitrogen in Pt/Fe(N)GR existed as pyridine N and N-Fe may be the key factor for its better initial ORR activity.The large surface area of BP,and the most of surface nitrogen existed in Pt/Fe(N)BP as graphite-N may be crucial to its best stability.