Modification based on internal refinement and external decoration: A powerful strategy for superior thermodynamics and hysteresis of Mg-Ni hydrogen energy storage alloys

The as-cast Mg-Ni alloy with nominal component Mg-10 wt%Ni (Mg10Ni) is successively modified based on the internal refinement by melt-spinning and external decoration through surface catalysis. The isothermal hydrogenation kinetics, absorption/desorption thermodynamics, hysteresis and non-isothermal desorption of modified Mg-rich alloys are investigated in this work. The results of modification indicate that the alloying and refinement microstructure are the foundation for high capacity and rapid kinetics. The active surface is the precondition to achieve the above-mentioned process. MWCNTs especially MWCNTs coupling with TiF₃ can easily activate the Mg-10 wt%Ni alloy and promote rapid absorption/desorption kinetics by H₂ dissociation and H-atoms auxiliary diffusion. Mg-rich Mg-Ni alloy after internal refinement and external decoration with MWCNTs and TiF₃ possesses superior thermodynamics and hysteresis. As high as 5.5 wt% hydrogen can be rapidly absorbed within 60 s and the endothermic peak is around 374 °C, which shifts toward low temperature as high as ∼75 °C than that of Mg-10 wt%Ni alloy without any catalysts. It is the synergistic catalytic effect originated from the assisted diffusion of MWCNTs and the surface spillover special effects of TiF₃ that promote the outstanding thermodynamics and hysteresis for Mg10Ni-MWCNTs-TiF₃.