Optimizing hydrogen ad/desorption of Mg-based hydrides for energy-storage applications

Hydrogen energy is expected to be an“ideal fuel”in the era of decarbonization.The discovery,de-velopment,and modification of high-performance hydrogen storage materials are the keys to the fu-ture development of solid-state hydrogen storage and hydrogen energy utilization.Magnesium hydride(MgH_(2)),with its high hydrogen storage capacity,abundant natural reserves,and environmental friend-liness,has been extensively researched.Herein,we briefly summarize the typical structure and hy-drogenation/dehydrogenation reaction mechanism of MgH_(2)and provide a comprehensive overview of strategies to effectively tune the thermodynamics and kinetics of Mg-based materials,such as alloy-ing,nanosizing,the introduction of additives,and composite modification.With substantial efforts,great achievements have been achieved,such as lower absorption/desorption temperatures and better cy-cling stability.Nonetheless,some pivotal issues remain to be addressed,such as unfavorable hydro-genation/dehydrogenation factors,harsh conditions,slow kinetics,incomplete dehydrogenation,low hy-drogen purity,expensive catalysts,and a lack of valid exploration of mechanisms in the hydrogena-tion/dehydrogenation process.Lastly,some future development prospects of MgH_(2)in energy-efficient conversion and storage have been presented,including advanced manufacturing ways,stabilization of nanostructures,the introduction of additives combined with structural modification,and utilization of advanced characterization techniques.

Modulated noble metal/2D MOF heterostructures for improved hydrogen storage of MgH_(2)

The conjugation of external species with twodimensional(2D)materials has broad application prospects.In this study,we have explored the potential of noble metal/2D MOF heterostructures in hydrogen storage.Specifically,the MgH_(2)-Ni-MOF@Pd system has shown remarkable hydrogen desorption/sorption performances,starting to liberate hydrogen at 1810C,which is 2300C lower than that of pristine MgH2.Under the catalytic effect of Ni-MOF@Pd,the dehydrogenation apparent activation energy of MgH2 is noticeably decreased from(133.5±17.5)to(34.58±1.87)kJ·moL^(-1),and the hydrogenation apparent activation energy is reduced from(70.41±7.43)to(25.78±4.64)kJ·moL^(-1),which is lowered by 63.4%.The fully-dehydrogenated MgH2-NiMOF@Pd composite rapidly uptakes hydrogen,with 2.62wt%at 100℃and 6.06 wt%at 150℃within 300 s,respectively.The mechanism analysis of MgH2 catalyzed by Ni-MOF@Pd has revealed that the transformation of Mg_2Ni and Mg_2NiH_4 could act as a"hydrogen pump",providing numerous channels for fast diffusion and transport of hydrogen atoms.Moreover,in the dehydrogenation process,the element Pd reacts with MgH_(2)to form the MgPd alloy phase,which makes MgH_(2)take precedence to decompose through the Mg-Pd alloy rather than self-decomposition,further reducing thermal stability and improving de/hydrogenation kinetics.The synergistic effect of Mg-Pd,Mg_2Ni,and the special ultra-thin 2D sheet structure of the additive is the main reason for the good hydrogen storage property of MgH_(2)-Ni-MOF@Pd.Our findings provide inspiration for designing efficient multifunctional additives with unique morphologies to optimize the hydrogen desorption/sorption behaviors of hydrogen storage materials.

Effect of micro-Al_(2)O_(3) powders on oxidation and corrosion behaviors of low-carbon MgO-C refractories

To solve the problem of poor high-temperature service performance caused by low carbonization of MgO-C refractories,low-carbon MgO–C refractories with excellent thermal shock,oxidation and corrosion resistances were successfully designed by using SiC whiskers as reinforcing phases and introducing micro-Al_(2)O_(3) powders as additives.The results indicated that the addition of micro-Al_(2)O_(3) powders optimized the internal structure of the material,like the columnar β-Si_(3)N_(4) with a stepped distribution and the mosaic structure formed between granular and flaky Mg_(2)SiO_(4),which synergistically strengthened and toughened the material and gave the material excellent mechanical properties and thermal shock resistance.Specifically,the cold modulus of rupture and cold crushing strength after thermal shock were increased by 4.1 and 20.3 MPa,respectively.Moreover,the addition of micro-Al_(2)O_(3) powders promoted the formation of fine particles of Mg_(2)SiO_(4),MgAl_(2)O_(4) and MgO,as well as a dense protective layer of Mg_(2)SiO_(4) in the material under high-temperature environment.Furthermore,spinel and high-temperature solid solution were formed in the corrosion environment.The oxidation and corrosion resistances were greatly improved by 41%and 15%,respectively.