Structure Manipulation Of Iron And Nitrogen Doped Carbon-based Composite Catalyst And Its Catalytic Performance For The Thermal Decomposition Of Ammonium Perchlorate

In order to achieve a higher combustion rate,ammonium perchlorate（AP）,an important oxidant in solid rocket propellants,is usually necessary to add catalysts to promote its thermal decomposition.Traditional catalysts are mainly transition metal oxides,while the lack of active sites greatly limits its catalytic performance.As a new type of catalyst with low preparation cost,high catalytic activity and green principles,carbon-based single atom has been widely used in various fields.In addition,the use of biomass to prepare its carbon support is low-cost and environmentally friendly,and the doping elements of biochar itself can also enhance the catalytic performance.Therefore,this study was using leftover rice as biomass raw material to prepare nitrogen-doped porous carbon material and sequentially loading iron particles of different sizes on this carbon material to prepare nitrogen doped carbon-based iron metal catalysts for thermal decomposition of AP and its mechanism research.The contents are as follows:Firstly,the remaining rice was used as the raw material for the large-scale manufacture of N-doped（nitrogen content 1.56%）porous carbon material with large specific surface area(1692.4 m²·g^-1)and pore volume(0.3588 m³·g^-1)by hydrothermal carbonization method.SEM（Scanning Electron Microscope）and TEM（Transmission Electron Microscopy）results showed that the carbon material was smooth spheres with the diameter of 2-7μm.The catalytic performance test of AP thermal decomposition indicated that the carbon material had certain catalytic performance:Compared with the thermal decomposition performance of pure AP,the high temperature decomposition tempurature decreased by 81.3℃and the exothermic heat increased by 561.9 J/g when the sample addition was 10 wt%.Secondly,nano-zero-valent iron（nZVI）was loaded on the surface of the nitrogen-doped porous carbon spheres to improve its catalytic performance.The loading amount of nZVI can be adjusted by different material addition ratios.XRD,SEM and XPS（X-ray Photoelectron Specteometer）results showed that nZVI had been successfully loaded on the surface of the carbon material by pyrolysis of the mixture of Fe Cl₃ and carbon material while the microscopic morphology of the carbon material did not change.The catalytic performance of AP thermal decomposition results suggested that the carbon material supported by nZVI had better catalytic performance for AP:the catalyst reduced the high temperature decomposition temperature of AP by 71.6℃,and the exothermic heat increased by 1163.7J/g when the sample addition amount was 10 wt%;compared with the unloaded carbon material,the exothermic heat of AP was further increased after loading nZVI.Finally,the size of the loaded metal nanoparticles was reduced to the atomic to further increase its catalytic performance.The iron phthalocyanine（Fe Pc）with a special molecular structure was selected as the iron source,and N-doped hierarchical porous carbon spheres loaded with single Fe atom were prepared by pyrolysis the mixtuere of carbon and Fe Pc at a high temperature of 800°C under N₂ atmosphere.XRD and Raman（Laser Raman Spectrometer）results showed that after loading single atom,the graphitization and crystallinity of the material were correspondingly improved;BET（N₂ Adsorption Analysis）results showed that the material appeared to be an obvious mesoporous structure and channels were formed between the different kinds of pores,which was more conducive to accelerating the reaction;XPS showed that the maximum loads of iron single atom reached to 0.93%,and there was Fe-N_X bond in the material along with the increase of the content of pyridine nitrogen,indicating that the single Fe atom was successfully loaded on the surface of carbon material.Catalytic performance studies showed that this material had excellent catalytic performance for AP thermal decomposition:when the amount of catalyst addition was 10%,the low temperature decomposition peak of AP disappeared,and only the high temperature decomposition peak at 295.9℃existed,and the exothermic heat increased by 1394.9 J/g,meanwhile,the activation energy was reduced by 208.7 k J/mol.The analysis results illustrated that the carbon-based iron single-atom catalyst had excellent catalytic performance due to its large specific surface area,multi-scale interconnected pore structure,high crystallinity and well-dispersed active sites.