Effect of Oxygen Impurities on Hydrogen Storage Properties of Mg80Ni16-xAlxY4(x=2,8)Alloys
The effect of oxygen impurities in hydrogen atmosphere on the hydrogen storage properties of Mg80Ni16-xAl,Y4(x=2,8)alloys was investigated,and the structural changed after hydrogen absorption/desorption cycles were characterized and analyzed.The results indicate that oxygen has a significant poisoning effect on the alloys,and the capacity decay rates of Mg80Ni14Al2Y4 and Mg80Ni8Al8Y4 alloys after 100 cycles are 49.2％and 40.4％,respectively.The alloys formed a large amount of MgO after cycling with oxygen atmosphere,and the significant reduction of the effective hydrogen storage phase is the main reason for the decrease in hydrogen storage capacity.In addition,although the oxidation did not affect the hydrogen absorption kinetics,the surface oxide layer inhibited the hydrogen release ability of the alloy,which is also an important factor leading to the reduction of the reversible hydrogen storage capacity of the alloy.The Mg80Ni8Al8Y4 alloy showed some improve-ment in its ability to resist oxygen poisoning due to the formation of a dense Al2O3 oxide layer favored by the higher Al content.Multiple hydrogen absorption and desorption treatments were carried out on the poisoned alloy under pure hydrogen conditions,namely reactivation.The results showed that reactivation had little effect on the poisoned alloy,and the reversible hydrogen absorption ability of the alloy could not be recovered.
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