Effect of ternary transition metal sulfide FeNi_(2)S_(4)on hydrogen storage performance of MgH_(2)

Hydrogen storage is a key link in hydrogen economy,where solid-state hydrogen storage is considered as the most promising approach because it can meet the requirement of high density and safety.Thereinto,magnesium-based materials(MgH_(2))are currently deemed as an attractive candidate due to the potentially high hydrogen storage density(7.6 wt%),however,the stable thermodynamics and slow kinetics limit the practical application.In this study,we design a ternary transition metal sulfide FeNi_(2)S_(4)with a hollow balloon structure as a catalyst of MgH_(2)to address the above issues by constructing a MgH_(2)/Mg_(2)NiH_(4)-MgS/Fe system.Notably,the dehydrogenation/hydrogenation of MgH_(2)has been significantly improved due to the synergistic catalysis of active species of Mg_(2)Ni/Mg_(2)NiH_(4),MgS and Fe originated from the MgH_(2)-FeNi_(2)S_(4)composite.The hydrogen absorption capacity of the MgH_(2)-FeNi_(2)S_(4)composite reaches to 4.02 wt%at 373 K for 1 h,a sharp contrast to the milled-MgH_(2)(0.67 wt%).In terms of dehydrogenation process,the initial dehydrogenation temperature of the composite is 80 K lower than that of the milled-MgH_(2),and the dehydrogenation activation energy decreases by 95.7 kJ·mol-1 compared with the milled-MgH_(2)(161.2 kJ·mol^(-1)).This method provides a new strategy for improving the dehydrogenation/hydrogenation performance of the MgH_(2)material.

Catalytic effect of MOF-derived transition metal catalyst FeCoS@C on hydrogen storage of magnesium

The introduction of the heterogeneous catalysts with high activity can significantly improve hydrogen storage performance of MgH_(2),therefore,in this paper,we synthesize a carbon-supported transition metal compound,FeCoS@C derivative from ZIF-67,by utilizing the in situ formed C dispersive multiphase Mg_(2)Co,α-Fe,Co_(3)Fe_(7),and MgS to implement catalysis to MgH_(2).Noteworthily,MgH_(2)-FeCoS@C rapidly ab-sorbs 6.78 wt%H_(2)within 60 s at 573 K and can also absorb 4.56 wt%H_(2)in 900 s at 473 K.Besides,the addition of FeCoS@C results in decreasing of the initial dehydrogenation temperatures of MgH_(2)from 620 to 550 K.The dehydrogenation activation energy of MgH_(2)decreases from 160.7 to 91.9 kJ mol^(-1).Studies show that the Mg_(2)Co,α-Fe,and Co_(3)Fe_(7)act as“hydrogen channels”to accelerate hydrogen transfer due to the presence of transition metals,and MgS with excellent catalytic effect formed from MgH_(2)-FeCoS@C provides a strong and stable catalytic effect.Besides,the carbon skeleton obtained by the carbonization of ZIF-67 not only serves as a dispersion for the multiphase catalytic system,but also provides more active sites for the catalysts.Our study shows that the multiphase and multiscale catalytic system provides an effective strategy for improving the hydrogen storage performance of MgH_(2).

Exploration of Rare-Earth Element Sc to Enhance Microstructure, Mechanical Properties and Corrosion Resistance of Zr-8.8Si Biomedical Alloy

The main mechanism of rare-earth element Sc on the microstructure and properties of Zr-8.8Si biomaterial alloy was explored.The novel Zr-8.8Si-xSc(x=0,5,10 and 15 at.%)alloys were prepared by electric arc smelting with Ar protection.The microstructural and mechanical properties as well as electrochemical corrosion and tribological behaviors in artificial saliva solution of the Zr-8.8Si-xSc alloys were systematically studied.The results show that the Zr-8.8Si-xSc alloys only consist of two-phase α-Zr and Zr_(3)Si,Sc dissolve in α-Zr matrix to form Zr-Sc solid solution.The addition of Sc is conducive to refine microstructure,and reduce micro-pores of Zr-8.8Si alloy which lead to higher Young's modulus,compressive strength and micro-hardness.Among them,the highest value of Young's modulus is 31.5 GPa,still at a low level in biomedical alloy.The promotion of corrosion resistance can be attributed to the addition of Sc which can accelerate the formation of passive film,slow down the appearance of pitting and reduce the accumulation of corrosion products in surface.Under the condition of sliding wear test with artificial saliva solution,compared with Zr-8.8Si-0Sc alloy,the wear loss of samples with Sc is greatly decreased,and wear resistance is increased with increasing content of Sc.The experimental results indicate that the combination of good mechanical properties,corrosion resistance and tribological properties of Zr-8.8Si-(5,10 and 15 at.%)Sc alloys was much better than Zr-8.8Si-0Sc alloy.Among them,the comprehensive property of Zr-8.8Si-10Sc alloy is preferable in this work.