Preparation And Research Of Carbon-coated Iron-based Catalysts In Electrocatalysis Performance

Faced with the continuous development and extremely severe overuse of globalized stone energy,the energy crisis will obviously become a potential hidden danger for the future development of mankind.Fuel cells and metal-air batteries are conversion devices for green,clean and safe energy.However,overpotential and slow kinetic processes for the cathodic reaction process were important bottlenecks that limited the performance of the batteries.It is urgent to find efficient catalysts to accelerate the reaction process.Carbon-coated iron-based catalysts has been favored by researchers due to its excellent electrical conductivity,lower cost,rich active sites and good stability.However,the large number of metal particles and carbon nanosheets stacked had seriously affected the structure and electrocatalytic performance of the materials.To solve these problems,a reasonable structure is used to design and construct by a simple and effective pyrolysis method to improve the electrocatalytic performance of the catalysts.The main contents of this paper are summarized as follows:Using resource-rich melamine and ferric chloride as raw materials,an electrocatalyst which coating metal nanoparticles with nitrogen-doped carbon nanotubes（Fe@NCNTS）was prepared by simple economy efficient pyrolysis strategies and process optimization.By investigating the effect of the ratio of reactants and pyrolysis temperature on the structure and activity of the catalyst,the most ideal fully encapsulated structure and the best electrocatalytic performance were analyzed.Under alkaline conditions,the initial potential and half-wave potentials of the best Fe@NCNTS samples were 0.968 V and0.808V,respectively,and the Tafel slope was 71 m V dec^-1.By the pore-forming agent ZnCl₂ template to modify the precursor,a stable three-dimensional structure catalyst（Fe@N-CNS/CNTS）with the coordination of carbon nanotubes and ultra-thin porous carbon nanosheets was successfully constructed.The three-dimensional structure gived the sample an extremely high porosity and effective specific surface area,thereby exposing a wealth of active sites.By adjusting the quality of ZnCl₂ and pyrolysis temperature,the structure and performance of the prepared catalysts were investigated.The optimal catalyst has onset potential of 0.983V,half-wave potential of 0.835V,Tafel slope of 63mV dec^-1,current density of only 7%after 25,000s aging test with a peak power density of 87.5 mV cm^-2.A three-dimensional catalyst consisting of nitrogen-doped graphene and hollow carbon nanotubes（Fe₃C@NGC）was prepared by a simple high-temperature pyrolysis and acid treatment process.Among them,phenanthroline inhibited the reunion of some metallic irons through complexation.The carbon nanotubes with FeN_x active sites distributed uniformly in the graphene carbon skeleton structure,both of which enhanced the stability of the catalyst.In addition,the edge defects of this composite structure further increased the catalyst’s oxygen reduction activity.The onset potential and half-wave potential of optimal catalyst were 0.984V and 0.825V,respectively.