Research On Fluoride-doped Carbon Catalysts For Cathodic Oxygen Reduction Reaction In Fuel Cells

Fuel cells,due to their green,clean and efficient characteristics,have become an important direction for the study of new energy applications and are regarded as the most promising new energy technology.However,the reaction kinetics of oxygen reduction reaction(ORR)on the fuel cell cathode is sluggish,and the high-efficiency catalyst is required to make the reaction effective.At present,platinum-based catalysts are commonly used,which limits the development of fuel cells,due to their high cost,scarcity,poor long-term stability and poisoning.Therefore,there is an urgent need to develop metal free ORR catalyst capable of replacing a platinum-based catalyst.In this work,polyvinylidene fluoride(PVDF)is used as a fluorine source for fluorine-doped catalysts for the first time,which provides a new strategy for the preparation of clean,low-cost and high-efficiency metal free ORR catalysts.Determined by element and electrochemical characterization of monofluoride-doped catalysts with different structural morphologies,a new type of nitrogen,fluorine double-doped microporous carbon nanofibers(N,F-MCFs)metal free ORR catalysts were successfully prepared by electrospinning,hydrothermal treatment,pre-oxidation and hightemperature carbonization of the three-component polymer of polyacrylonitrile/ polyvinylidene fluoride/ polyvinylpyrrolidone(PAN/PVDF/ PVP).The contents of each chapter are as follows:The first chapter introduces the fuel cell overview,the kinetic history of oxygen reduction reaction,the research progress of oxygen reduction reaction catalyst and the main work and significance of this paper.The second chapter mainly introduces the experimental reagents,experimental equipment,test instruments,test methods and calculation methods used in this paper.In the third chapter,by adjusting the different structural morphology of PVDF precursors,three kinds of monofluoride-doped catalysts(F-powder,F-fibers,F-membrane)were prepared to explore their different morphological structures and ORR catalysis.The influence relationship of performance provides a theoretical support for the preparation of the postnitrogen and fluorine double-doped catalysts.In the fourth chapter,Fluorine double-doped microporous carbon nanofiber catalyst(N,F-MCFS)was successfully synthesized by electrospinning,hydrothermal treatment,pre-oxidation and hightemperature carbonization of the polyacrylonitrile/ polyvinylidene fluoride/polyvinylpyrrolidone(PAN/ PVDF/ PVP)three-component polymer.Its preparation conditions and structure morphology were characterized,and the most suitable preparation conditions were explored.The series of nitrogen and fluorine double-doped microporous carbon nanofibers(N,FMCFs)were tested for electrochemical performance,and their ORR reaction paths were judged to find the most excellent metal free ORR electrocatalysts.The fifth chapter summarizes the full text.