| With the decline of fossil fuels,there is a global research boom on renewable energy and energy conversion technologies.In the field of fuel cells and zinc-air batteries,the catalytic activity,lifetime,and cost of negative catalyst materials have become bottlenecks that limit the development of energy storage devices.Usually,the main catalysts used in the negative electrode of batteries are platinum-based precious metals,but the high price,easy poisoning,and poor cycling stability limit their large scale commercial application.Therefore,it is of great significance to research and develop catalysts with low cost and high catalytic activity and stability to replace precious metal catalysts.In this thesis,materials with excellent oxygen reduction catalytic activity were prepared using graphene,which is rich in defects and oxygencontaining functional groups and easily anchored and loaded with metal nanoparticles,as a substrate and nitrogen doped in a high-temperature ammonia gas environment.The main research results are as follows.Firstly,in this thesis,a series of nitrogen-doped graphene-loaded metal nanoparticle catalyst samples were prepared using a simultaneous pyrolysis method with metal source selection studies around different metal salt compounds and metal organic compounds,and the effects of different transition metal Fe,Co and Ni compounds on the morphology and structure of the materials were discussed.Compared with metal chlorides,ferrocene(Fc)and cobaltocene as precursors are easy to obtain nanoparticles with more uniform dispersion and smaller scale,and the prepared materials have higher density of active sites,and the pyridine nitrogen content reaches 38% after thermal decomposition in high temperature ammonia atmosphere.The metal elements in the material existed in various forms such as oxides and carbides,among which the half-wave potential of Fc was 0.778 V and the number of transferred electrons was 3.45,and the catalytic performance was better than that of the sample with metal chloride as the precursor.Then,a series of iron-based@nitrogen-doped graphene materials(Fex N@NG)were prepared by simultaneous pyrolysis experiments in ammonia and argon atmospheres using diacetyl ferrocene as the precursor metal source and graphene oxide as the substrate,and the modulating effects of the pyrolysis temperature and the ratio of precursors used on the nitrogen doping and pore structure of the catalysts were discussed.The results showed that the pyridine nitrogen and Fe-N contents of the sample Ac Fc@GO5 were relatively high at the pyrolysis temperature of 700 °C and the mass ratio of transition metal to graphene oxide of 1:5,where the metal nanoparticles with core-shell structure loaded on reduced graphene oxide exhibited high unit catalytic activity and possessed the optimal oxygen reduction catalytic performance under the joint action of graded pore structure.Finally,the optimum temperature and ratio samples obtained were treated by plasma technology to explore the effects of treatment time and treatment power in oxygen atmosphere on the structure and catalytic performance of the materials.The results showed that the optimal catalytic performance was obtained at a treatment time of 10 s and a treatment power of 100 W.The half-wave potential was 0.842 V and the Tafel slope of P100W-O2 was 87.68 m V/dec,which was slightly lower than that of 86.72 m V/dec for 20% Pt/C.In addition,extended research on the treatment atmosphere was carried out,using Ar and NH3 for treatment.When the treatment time is 30 s,the material has a higher oxygen defect or Fe-N content,and has a higher half-wave potential and current density than the original. |
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