Research On Hydrogen Storage Performance Of Mg₉₆La₃Ni Ternary Alloy

In the past few decades,the excessive consumption of traditional fossil fuels has directly caused the shortage of fossil fuels and various global problems that threaten human survival.Therefore,it is imperative for countries all over the world to develop new types of renewable energy to replace fossil fuels.Compared with other renewable energy sources,hydrogen energy is cleaner,and it is easy to convert with electrical energy.It has become the hottest new energy source in the field of scientific research,and magnesium-based hydrogen storage alloys have become One of the preferred options for hydrogen storage materials.So far,magnesium-based hydrogen storage alloys have developed three series,including pure magnesium series,magnesium nickel series and rare earth magnesium series.A large number of experiments have confirmed that adding a catalyst during the ball milling of the alloy can greatly improve the hydrogen absorption and desorption properties of the alloy.Based on this,the research object selected in this paper is the rare earth magnesium Mg₉₆La₃Ni hydrogen storage alloy,focusing on the effect of ball milling process and the addition of catalyst on the hydrogen absorption and desorption kinetics and thermodynamic properties of the alloy.PVP and nitrate are prepared by a combination of chemical precipitation and high-temperature foaming to prepare a C-supported metal nanoparticle composite catalyst.Nanoparticles with a particle size of 20-50 nm can be obtained embedded in a carbon layer with a thickness of less than 12 nm.Raman spectroscopy can be seen that the carbon layer of the composite catalyst has a relatively high defect density,which will facilitate nucleation during hydrogen absorption and desorption.According to the data XRD,this catalyst is mainly composed of amorphous carbon.Samples of Mg₉₆La₃Ni alloy with different ball milling times were prepared using a planetary ball mill.The ball milling times were 1h,5h,10h,15h and 20h.Prolonging the ball milling time will increase the amorphous phase in the alloy and reduce the amount of H₂ storage.The rate of H₂ storage and release is first and then slow.The activation energy of H₂ release is 107.14 kJ/mol,91.96 kJ/mol,110.982 kJ/mol,106.57 kJ,103.887kJ/mol H₂ respectively;hydrogenation enthalpy change?H was 81.54 kJ/mol,79.8kJ/mol,89.84 kJ/mol,80.12 kJ/mol,79.66 kJ/mol H₂.The results showed that the sample with a ball milling time of 5h had the best performance,and the reversible H₂ storage capacity reached 6.4 wt.%?Finally,a 5h ball milling process was selected,compounding Mg₉₆La₃Ni alloy with5 wt.%Catalyst.Experiments have shown that different recombination times have different effects on the hydrogen storage properties of Mg₉₆La₃Ni alloy.Analysis shows that long-term recombination will destroy the lamellar structure of the catalyst,causing it to reduce nucleation energy and reduce defects.Ball milling time will make the carbon sheet structure into a block,which affects its catalytic function.Choosing a recombination time of 1h,the activation energy of hydrogen release was reduced to 76.42 kJ/mol,and the kinetic performance was improved,but its thermodynamic performance was not greatly improved.