Synthsis Of Oxygen Reduction Catalyst And Preliminary Studies On Mechanism Of Oxygen Reduction Reaction

With the increasingly serious problem of energy shortage and environmental pollution,the development of clean and efficient new energy devices has become an important task for the future development of mankind.Among kinds of new energy devices,lithium-air battery has got widely and increasing attention because of its high theoretical capacity,environmental friendliness and other characteristics.However,the kinetics of the Oxygen Reduction Reaction(ORR)at the cathode of the lithium-air battery is extremely slow,especially without the helping of oxygen catalysts,which affects the discharge capacity of the full battery,and become one of the main reasons why the batteries above have not been commercialized on a large scale.The work of this paper focuses on the basic researches related to oxygen reduction reaction,mainly focusing on the exploration of oxygen reduction mechanism of different catalytic materials,and the exploration and verification the strategies for enhancing the electrocatalytic performances of oxygen reduction catalysts.The specific work includes the following three parts:1.Three kinds of single crystal Fe3O4 nanoparticles with different morphologies and crystal planes were synthesized by hydrothermal/solvothermal method,and their surface crystal surfaces were determined by XRD and other physical characterizations,which are three basic crystal surfaces of[111],[100]and[110].Then,the catalytic activity of Fe3O4 on different basic crystal surfaces was analyzed by RRDE and other methods,and the relationship between the difference of catalytic activity and surface structure effect was analyzed and speculated.2.Polymers and iron-based metal salts were spun into nanofibers by electrospinning technology,and metal(Fe,Co,Ni)@nitrogen-doped carbon nanofibers composites were prepared by one-step calcination.Through the analysis of XPS and other physical characterization results,we found that the structure of the three nanofibers is basically the same,and there are abundant chemical bonds between metal elements,carbon and nitrogen elements.Next,the oxygen reduction performance was analyzed by RDE and compared with the intrinsic oxygen reduction catalytic activity of pure nitrogen doped carbon fibers and elements ORR activity on the well-known volcanic maps,and the relationship between the difference of oxygen reduction activity and electronic structure effect was analyzed and discussed.3.The gold disk electrode was roughened by traditional electrochemical roughening method.The oxygen reduction process in the electrolytes saturated with oxygen at different pH values electrolytes(0.1 M KOH,0.1 M NaClO4 and 0.1 M HClO4)was characterized by in-situ electrochemical Surface Enhanced Raman Spectroscopy(SERS)method.By analyzing the variation of the Raman peak intensities of intermediate products of O2-and H2O2 with potential scanning,the reaction pathways and the effect of electrolyte pH value on the reaction pathways were discussed and speculated.