Study On Preparation And Electrochemical Performance Of New Fuel Cell Catalysts

Hydrogen energy is a kind of clean,renewable and efficient energy.It is an ideal sustainable energy which can replace fossil energy.Proton exchange membrane fuel cells（PEMFC）,as a new type of energy conversion device,can continuously and efficiently convert hydrogen energy into electricity at a low operating temperature.In principle,it is equivalent to the reverse reaction of water electrolysis,and no pollutants are generated.PEMFC is one of the most promising power sources used in electric vehicles and fixed power stations.The two sides of the proton exchange membrane are respectively composed of hydrogen and oxygen gas electrodes to form the anode and cathode,through the diffusion layer to the catalytic layer and proton exchange membrane interface for oxidation and reduction reactions.In the present study,the noble metal platinum（Pt）is the catalytic material with the best catalytic activity and high stability,regardless of anode or cathode.The slow kinetics of oxygen reduction reaction（ORR）at the cathode and the high cost of platinum-based catalyst materials are the important factors restricting the commercialization and popularization of PEMFC.Therefore,the development of high-performance catalysts with low platinum and non-precious metals and the enhancement of catalyst durability have become urgent scientific problems to be solved,and the evaluation of catalyst performance cannot be done without electrochemical analysis methods.In this paper,electrochemical analysis technology as the main means to evaluate the performance of new cathode ORR catalyst,so as to carry out the following work:（1）Preparation and performance evaluation of sulfonated porous carbon supported Platinum nanoparticles（Pt/KB-SO₃H）catalystsBy depositing Pt nanoparticles inside the porous carbon and conducting external sulfonation treatment to reduce the amount of Nafion,proton conduction within the catalyst layer can be improved without affecting the transmission of O₂.In addition to improving the utilization rate of Pt,ORR efficiency of fuel cell cathode can be improved.The materials were characterized by transmission electron microscopy（TEM）,Energy dispersive X-ray microscope（EDX）and X-ray photoelectron spectroscopy（XPS）.The kinetic properties of the sulfonated porous carbon supported Pt catalytic system were systematically investigated by rotating electrode（RDE）test method.The results showed that Pt/KB-SO₃H exhibited better ORR performance and active specific surface area than the commercial Pt/C catalyst（TKK）in half cells.（2）Preparation and performance evaluation of Graphene-supported platinum-nickel alloy nanoparticles（Pt Ni/graphene）catalysts by electrodepositionPlatinum-nickel alloy nanoparticles were electrodeposited onto graphene carrier to prepare platinum-nickel nanoparticles electrocatalysts by electrochemical deposition.The Pt Ni/graphene electrocatalysts were characterized by high resolution electron microscopy（HRTEM）,energy dispersive X-ray microscopy（EDX）,X-ray diffractometry（XRD）,X-ray photoelectron spectroscopy（XPS）and Raman spectroscopy.The results show that the morphology and composition of Pt Ni nanoparticles on graphene are controllable.The electrocatalytic properties of Pt Ni/graphene for oxygen reduction reaction（ORR）were systematically studied,showing similar kinetic properties.In addition,graphene during electrodeposition leads to carbon vacancies and defects,increasing the interaction between nanoparticles and graphene,thereby limiting the aggregation of nanoparticles to enhance point catalytic stability,which was verified by accelerated decay tests.（3）Preparation and performance evaluation of Fe-N-C（IL@Fe-N-C）catalyst for ionic liquid deposition by sequential depositionNon-precious metal catalysts have abundant raw materials and low prices,among which Fe-N-C catalysts show high oxygen reduction activity and attract much attention.However,their low center density and the formation of intermediate products lead to the lack of long-term durability in proton exchange membrane fuel cells.Ionic liquid（IL）with high oxygen solubility,high proton conductivity and high hydrophobicity can promote oxygen transport in the pore of the material,reduce the overpotential of oxygen reduction reaction and promote the four-electron oxygen reduction reaction.The IL@Fe-N-C composite catalytic system was prepared by simple and mass-produced sequential deposition method.The properties of IL were used to improve the four-electron oxygen reduction reaction of Fe-N-C catalyst,reduce the yield of hydrogen peroxide,improve the electrochemical activity and increase its durability.