| dc.description.abstract | Climate change has impelled humanity to seek renewable alternative energy sources, aiming to reduce dependence on fossil fuels and mitigate environmental impacts. Hydrogen energy, as a clean and renewable form of energy, has emerged as a critically significant research topic of global prominence. However, low volume density and high flammability of hydrogen make its storage and transportation difficult. In this regard, the development of materials with high hydrogen storage capacity has become a popular research field.
AB5 alloy is a commonly used solid hydrogen storage alloy, where A is mainly rare earth metals such as lanthanides, and B is usually transition metals such as nickel. However, due to the increasing price and scarcity of rare earth metals, in this study, La–Ca–Mg–Ni-based AB3 hydrogen storage alloys have been proposed to partially replace AB5 alloys. A series of AB3-type La–Ca–Mg–Ni-based hydrogen storage composites with different ratios were prepared by vacuum induction melting, and heat treatment at 1000°C for 12 hours under an argon atmosphere. Inductively Coupled Plasma (ICP) was used to determine the alloy composition as La0.7Ca0.67Mg1.32Ni9. Electron Probe Micro-Analysis (EPMA) showed a significant improvement in chemical homogeneity after the heat treatment. The X-ray diffraction analysis revealed the presence of two phases in the alloy, namely the (La, Mg)Ni3 phase and the LaNi5 phase. Using the Pressure-Composition-Isotherm (PCI) method based on the Sieverts law, the hydrogen storage capacity of pure AB3 was found to be 1.54 wt% at 25°C, under a hydrogen charging pressure of 5 MPa. The PCI curve of the AB3 obtained shows a flat pressure plateau, thus suggesting a high homogeneity of the alloy prepared in this study. In contrast, the PCI curve of the commercial AB5-type La0.6Ce0.4Ni5 hydrogen storage alloy has a higher plateau pressure, with a bigger hysteresis. However, the final hydrogen storage capacity of these two alloys were similar at 1.54 wt% for AB3, and 1.45 wt% for AB5. In terms of composites, different ratios of AB5 (20, 40, 50, 60 and 80 wt%) were composited into AB3-type La–Ca–Mg–Ni-based hydrogen storage alloy. In all of AB3-type La–Ca–Mg–Ni-based composites, the hydrogen storage capacities were nearly the same, about 1.4~1.43 wt%. Among all of composites, the one consisting of 50 wt% of AB5 had the highest hydrogen content of 1.43 wt%. However, the difference was not significant, and all these hydrogen contents obtained were lower than that of the pure AB3 alloy. Finally, the different conditions of high-temperature activation have been performed on pure AB3 and composite with 50 wt% of AB3 and 50 wt% of AB5. The hydrogen storage capacities obtained at 7 MPa were 1.64 wt% and 1.8 wt% respectively, indicating that both alloys successfully increased their hydrogen storage capacities through high-temperature activation conditions. In terms of hydrogen storage capacity, the results also suggested the possible beneficial effect of blending AB3 and AB5. | en_US |