| Hydrogen has been considered as an alternative energy carrier with the potential to promote the transformation of fossil fuel to clean energy because of its outstanding advantages such as high energy density,many potential energy types,light weight and little impact on the environment.One of the main obstacles to the expected future hydrogen economy is the lack of safe,efficient and economic vehicle hydrogen storage.Nano Mg-based materials,which have high energy density,low cost and can overcome the defects of traditional hydrogen storage materials in thermodynamics and dynamics,are considered as the best choice for hydrogen storage materials.However,the formation of Mg O or Mg(OH)2 layer on the surface of Mg O is easy to hinder the permeation of hydrogen in the material.Therefore,in this paper,nano Mg-based composite materials(powder and thin-film nano Mg-based composite)have been prepared,their hydrogen storage properties are studied preliminarily,and the following results are obtained:(1)The air-stable polymethylmethacrylate(PMMA)-Mg NPs composite was synthesized by wet chemistry approach.Through PMMA self-assembly coating and optimization of process conditions,air-stable Mg NPs with an average diameter of 5 nm were synthesized in sol PMMA,the synthesis mechanism was explored,and the interface binding model was established;CH3Mg Cl is firstly used as the precursor of organic magnesium to prepare the nanocomposite with mild preparation conditions.The results show that PMMA could not only disperse Mg NPs and block the infiltration of oxygen and water molecules in the air,but also affect the growth,morphology,size and hydrogen storage capacity of Mg NPs.(2)Without adding catalyst,at 200 ℃ and H2 of 30 bar,the PMMA-Mg NPs composite can absorb hydrogen rapid in 8 min,The amount of hydrogen absorb 4.8 wt% within 30 min,then release 4.15 wt% at 270 ℃ and 0 bar within 25 min.The higher hydrogen storage capacity,faster hydrogen absorption/dehydrogenation rate,stable H2 absorption/desorption reversible cycles,which have been realized.(3)In order to improve the thermodynamic and kinetic properties of hydrogen storage,multi walled carbon nanotubes(MWCNTs)were added,MWCNTs-PMMA-Mg NPs composite was synthesized by wet-chemistry approach.Mg NPs with an average size of 3.6 nm were directly reduced on the MWCNTs-PMMA template.The addition of MWCNTs would limit the growth of Mg NPs and further reduces the particle size of Mg NPs;PMMA can effectively prevent Mg NPs from peeling off the nanotube;When the mass ratio of CH3 Mg Cl,PMMA and MWCNTs is 4:2:1,the maximum loading rate of Mg NPs is 82%.(4)The hydrogen storage properties of MWCNTs-PMMA-Mg NPs composite were studied.Without adding catalyst,at 200 ℃ and hydrogen pressure of 20 bar,hydrogen absorption increased sharply in 5 min,the amount of hydrogen absorption can be increased to 6.7 wt% within 20 min,and the mass fraction of hydrogen released at 150 ℃ and 0 bar is 3.7 wt%.Compared with PMMA-Mg NPs,MWCNTs-PMMA-Mg NPs has higher hydrogen storage capacity,lower temperature and pressure of H2 absorption/desorption,more rapid H2 absorption/desorption rate.(5)Considering the poor thermodynamic properties of thin-filmed hydrogen storage materials,Mg/C:H plasma polyethylene nanocomposite is synthesized through the combination of magnetron sputtering with grazing angle deposition(MS-GLAD)and plasma-enhanced chemical vapor deposition(PECVD),and the modeling research of Kinetic Monte Carlo(KMC)was carried out.the morphology of Mg thin film can be modified by controlling the deposition angle and sputtering pressure.(6)In the same reactor,C:H plasma polyethylene thin film(PPF)is synthesized by PECVD from ethylene precursor aiming to conformally cover the nano Mg and protect them against oxidation.The deposited rate,mechanical properties,the cross-linking density,and corrosion resistance of the C:H layers can be effectively controlled by adjusting the RF power,and optimizing the physical and chemical properties of the coating. |
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