The Study Of The Performance Of Non-precious Metal Oxygen Reduction Reaction Catalysts With Ribose As Carbon Resource

In many energy conversion and storage devices,oxygen reduction reaction(ORR)is an important reaction,in which fuel cells are the most representative.However,because the fuel cell requires platinum Pt or Pt-based material as a catalyst,so its cost is a big drawback.Therefore,in order to reduce the cost of the battery and realize the commercial development of the fuel cell,it is necessary to find an inexpensive and efficient oxygen reduction catalyst which can replace platinum.In the research of non-platinum catalysts,the catalyst based on nitrogen-doped graphene material is inexpensive and superior performance,and it is a new type of catalyst which is considered to be substituted for platinum.In this paper,a new method for the preparation of nitrogen-doped graphene materials is studied.The caramel precursor is used as a pre-reaction of pyrolysis using a Maillard reaction between the amino group and the carbonyl group,after which the caramel is mixed in the molten salt for secondary pyrolysis,once in nitrogen gas and once in ammonia gas.The synthesized nitrided graphene material has a larger surface area and has a large number of micropores,and the active site density of the catalyst surface is also improved,thereby improving the oxygen reduction performance of the catalyst.And after the second high temperature pyrolysis the material has a good thermal stability and conductivity.First,we use ribose and ammonium chloride as precursors,sodium chloride,potassium chloride as a mixed salt to prepare nitrogen-doped graphene catalyst.The prepared catalyst was a metal-free microporous nitrogen-doped graphene(MNG).The surface morphology of the catalytic material is microporous nitrogen doped graphene,and the BET analysis shows that the highest specific surface area is 1261 m2·g-1 and has a large number of micropores.This microporous structure provides a number of defects,resulting in a large number of active sites,while the diffusion of O2 is conducive to improve the oxygen reduction of dopant graphene and microporous nitrogen stability.Thus,when used as a cathode material for a fuel cell,the power density of the fuel cell reaches 547 mW·cm-2 at one atmospheric back pressure and decreases by only 12.5%after 250 hours,and the stability is good.The catalyst has a good performance in the metal-free oxygen reduction catalyst and is expected to be a commercial oxygen reduction catalyst.Carbon nanotube(CNT)also has high specific surface area,high crystallinity,excellent conductivity and high electrochemical corrosion resistance,and has great potential as a supporting material for excellent catalysts in carbon materials.Fe-N-C-doped CNT catalysts exhibit strong ORR activity in acidic media.The pyrolysis of the CNT can lead to the growth of the nanotubes necessary for the Fe atoms on the CNT surface.The pore structure on the CNT should be able to improve the mass transfer of O2,protons and water to increase the power density of the proton fuel cell.In order to improve the performance of the catalyst,the carbon nanotubes supported by the catalyst,we added the iron salt precursor in the experimental step to synthesize the carbon nanotubes.The change in the morphology and properties of the catalyst was explored by varying the amount of iron in the precursor.From the SEM and TEM characterization,when the iron salt was added,the morphology of the catalyst changed from nanosheets to carbon nanotubes.After analyzing the Raman spectra,it was found that the D/G peak ratio of the catalyst with the best ORR performance was 0.98 and the micropore defects were more,which indicated that the active sites of the catalysts were more favorable and the performance of the ORR was improved The The characterization of XRD shows that the carbon in the synthesized catalyst is amorphous carbon.In the catalyst of carbon material,amorphous carbon has better activity and stability than graphite carbon.Electrochemical characterization found that the best performance of ORR catalyst has the highest starting potential of 0.95 V,after 10100 cycles,the potential drop only decreased by 38 mV.The catalyst has better oxygen reduction properties and is expected to be used as a platinum catalyst for the commercialization of fuel cells.