Preparation Of Fluorine-Doped Graphene-Based Composites And Their Catalytic Activity In Thermal Decomposition Of Ammonium Perchlorate

In this paper,fluorine-doped graphene materials with different F-doping contents were prepared by hydrothermal synthesis.On this basis,fluorine-doped graphene-supported copper oxide and lead oxide composites were further prepared by using simple chemical deposition method and in-situ self-assembly growth method and applied to the catalytic thermal decomposition of ammonium perchlorate.First,using graphene oxide（GO）as raw material and trifluoroacetic acid（CF₃COOH） as fluorine source,graphene materials（F-GO）with different F doping contents were prepared by hydrothermal synthesis.The fluorine source concentration,temperature and time in the preparation process were changed by the control variable method,and the prepared F-GO was optimized and screened.The optimization experiment shows that when the concentration of fluorine source is 50%,the reaction temperature is180°C,and the reaction time is 24 h,the surface defect of the prepared F-GO is the largest,and the doping amount of fluorine can reach up to 5.03%.By comparing the structure and morphology of graphene materials before and after F-doping,it was found that F-doping would destroy the original smooth surface of graphene and increase the surface defects and layer spacing of graphene,which mainly existed in the form of C-F covalent bond,semi-ionic component and covalent bond.Secondly,combined with experiments and simulation calculations,it can be seen that,on the one hand,the doping of F increases the hydroxyl content on the surface of graphene and the surface active sites,which can effectively catalyze the pyrolysis of AP.When 10%F-GO is added,the high temperature decomposition peak temperature of AP can be decreased by 156.7℃,and the apparent decomposition heat can be increased by 3657.7 J/g.On the other hand,the incorporation of F can accelerate the transfer of H in the process of AP pyrolysis,reduce the reaction energy barrier,and make the mixture gradually generate a macroporous structure during the reaction process,stabilizing or reducing the energy of the reaction system,which is beneficial to the continuous stability of AP decomposition.Then,using F-GO as the carrier,by adjusting the p H value of the solvent,F-doped graphene-supported CuO with different loading morphologies of nanocubic CuO,nanoparticle CuO,and nanorod CuO was prepared,and the CuO loading rate was about20%composite catalyst.The material characterization results show that when the p H value is 12,the F-GO supported nanorod-like CuO composites have a minimum particle size of about 10-20 nm.Compared with pure AP and AP-added F-GO supported nanocubic CuO and nanoparticulate CuO,the highly dispersed nanorod-like CuO particles and mesoporous structure provide more reactive sites in the catalytic pyrolysis of AP.The performance of F-GO supported nanorod-like CuO to catalyze the pyrolysis of AP is the best.When adding 3 wt.%nanorod-like F-GO/CuO,the peak temperature of AP pyrolysis decreases by 117.4℃,and the apparent heat of decomposition increases from 603.5 J/g to 3813.2 J/g.Finally,using GO as the initial raw material,hydrazine hydrate as the reducing agent,and CF₃COOH as the fluorine source,the fluorinated reduced graphene（F-r GO）material was prepared by hydrothermal method,and then acrylamide（AM）was used as the complexing agent.F-doped graphene-supported lead oxide nanocomposites（F-r GO/Pb O）with highly dispersed particles were prepared by in-situ self-assembly method.It is found that the addition of AM during the preparation process can effectively improve the dispersibility of the supported metal particles.The results of AP pyrolysis experiments show that the addition of 3 wt.%F-r GO/Pb O composite can reduce the high temperature decomposition peak temperature of ammonium perchlorate（AP）by 125.3°C,advance the initial decomposition temperature by 30.3°C,and increase the apparent decomposition heat release about 6 times,its excellent catalytic performance mainly comes from the large specific surface area and high dispersibility of Pb O nanoparticles provided by the unique two-dimensional structure of graphene.