Magnesium-based Hydrogen Storage Materials Synergisticly Optimized By Multi Components

This paper first discusses the Mg based hydrogen storage alloy research and development,and introduces the method to improve the hydrogen storage properties,starting from alloying by solution of Mg₂Ni_1-xTi_x was prepared by sintering（x=0.08,0.12,0.16）alloys,effects of different content of Ti element in Mg₂Ni alloy Chuqing the performance improvement of thermodynamic properties of alloys and reduce the hydrogen storage capacity,after the two chapter,we made Ni@TiO₂ and Ni-based@G catalysts were synthesized,and MgH₂ composite,to further explore the effect of two kinds of catalysts on hydrogen storage performance of MgH₂.The composition and structure of the phase were analyzed by scanning electron microscope（SEM）and X ray diffraction（XRD）.The thermodynamic properties of hydrogen absorption and desorption were analyzed by Sievert method.The following conclusions are drawn:（1）solid solution sintering method can be used to prepare high purity Mg₂（Ti,Ni）phase Mg₂Ni type alloy,and its purity is as high as 98 wt%,and the alloy has good performance of hydrogen absorption and desorption.Ti solid solution significantly improved the dynamic properties of Mg₂Ni alloy,and the activation energy of Mg₂Ni_1-xTi_x（x=0.08,0.12,0.16）was62.8 kJ/mol,59.4 kJ/mol,63.8 kJ/mol,respectively,which was lower than that of pure Mg₂Ni.The apparent activation energy（Ea）was 69 kJ/mol.In terms of thermodynamic performance,the performance is also slightly improved.The enthalpy change of hydrogen evolution of Mg₂Ni_1-xTi_x（x=0.08,0.12,0.16）is 63.6 kJ/mol H₂,62.3 kJ/mol H₂,64.5 kJ/mol H₂,which is lower than that of ball milling pure Mg₂Ni（ΔH_d=65 kJ/mol H₂）.（2）Ni@TiO₂ nano catalyst has been successfully prepared by hydrothermal method.We can observe the distribution of Ni particles on TiO₂ nanorods,and then explore the best process of 400 RMP,ball milling 20 h and MgH₂ ball milling to get MgH₂-5wt%Ni@TiO₂ composite hydrogen storage materials.MgH₂-5wt%Ni@TiO₂ begins to place hydrogen at 250°C and basically ends hydrogen at 330°C.The hydrogen release temperature is 160°C earlier than that of MgH₂.The activation energy of the hydrogen release of MgH₂-5wt%Ni@TiO₂ is 126.6kJ/mol,which is much lower than that of pure MgH₂ by 158.5 kJ/mol for the activation energy of hydrogen.After 30 cycles,the amount of hydrogen released from MgH₂-5wt%Ni@TiO₂ still reaches 81%of the initial hydrogen release,which indicates that the material has certain stability in hydrogen absorption and desorption,and has certain practical application value.（3）the preparation of Ni@G,CoNi@G and MgH₂ composite catalyst,MgH₂-5wt%Ni@G and MgH_2-5wt%CoNi@G,MgH₂-5wt%Ni@G can obviously improve the dynamic performance of pure MgH₂,compared with the pure MgH₂ dehydriding temperature of 175°C in advance,MgH₂-5wt%Ni@G and MgH₂-5wt%CoNi@G desorption activation energy was122.2 kJ/mol and 131.2 kJ/mol,better than MgH₂ hydrogen activation 158.5 kJ/mol.In comparison to pure MgH₂,the thermodynamic perforamnce of MgH₂-5wt%Ni@G was slightly improved as its dehydriding enthalpy change was reduced to 74.1 kJ/mol H₂ from 76 kJ/mol H₂.