The present work primarily investigates the morphological evolution of the body-centered-cubic (BCC)/B2 phases in Al_xNiCoFeCr high-entropy alloys (HEAs) with increasing Al content. It is found that the BCC/B2 coherent morphology is closely related to the lattice misfit between these two phases, which is sensitive to Al. There are two types of microscopic BCC/B2 morphologies in this HEA series: one is the weave-like morphology induced by the spinodal decomposition, and the other is the microstructure of a spherical disordered BCC precipitation on the ordered B2 matrix that appears in HEAs with a much higher Al content. The mechanical properties, including the compressive yielding strength and microhardness of the Al_xNiCoFeCr HEAs, are also discussed in light of the concept of the valence electron concentration (VEC).

As a promising hydrogen storage material, sodium borohydride (NaBH₄) exhibits superior stability in alkaline solutions and delivers 10.8 wt.% theoretical hydrogen storage capacity. Nevertheless, its hydrolysis reaction at room temperature must be activated and accelerated by adding an effective catalyst. In this study, we synthesize Co nanoparticles supported on bagasse-derived porous carbon (Co@xPC) for catalytic hydrolytic dehydrogenation of NaBH₄. According to the experimental results, Co nanoparticles with uniform particle size and high dispersion are successfully supported on porous carbon to achieve a Co@150PC catalyst. It exhibits particularly high activity of hydrogen generation with the optimal hydrogen production rate of 11086.4 mL_H2∙min⁻¹∙g_Co⁻¹ and low activation energy (E_a) of 31.25 kJ mol⁻¹. The calculation results based on density functional theory (DFT) indicate that the Co@xPC structure is conducive to the dissociation of [BH₄]⁻, which effectively enhances the hydrolysis efficiency of NaBH₄. Moreover, Co@150PC presents an excellent durability, retaining 72.0% of the initial catalyst activity after 15 cycling tests. Moreover, we also explored the degradation mechanism of catalyst performance.

The research and development of new high capacity hydrogen storage materials is of both academic significance and practical importance. LiBH₄ has been attracting extensive attention because of its high gravimetric and volumetric hydrogen contents, but its practical applications are hindered by high thermal stability, sluggish kinetics, and relatively high operating temperatures. Doping with catalysts is a key strategy and important research direction to solve these problems. Here, various catalysts and their performances in the dehydrogenation of LiBH₄ are summarised. The catalytic mechanisms of different catalysts are also outlined. In addition, NH₃BH₃ has been drawing much attention due to its high hydrogen capacity and environmental friendliness. Release of hydrogen from NH₃BH₃ by hydrolysis can proceed at room temperature with appropriate catalysts. The effects of diverse catalysts on the hydrogen evolution of NH₃BH₃ hydrolysis are also reviewed. Some prospective aspects for research and development of hydrogen storage materials are also proposed in this review.