*4.1. AB*<sup>5</sup> *Type Hydrogen Storage Alloy*

In 2001, G. Liang et al. [96] began to synthesize LaNi5 using two MA pathways. The first one is the mechanical alloying of La powder and Ni powder, and the second one is the mechanical milling of LaH with Ni. They all result in the formation of the *α*-LaNi5 hydride phase. After testing, the H2 storage performance of the two types of LaNi5 is similar to that of the melted bulk LaNi5. Another disadvantage of the AB5 alloy is that it is susceptible to all kinds of pollution. Improving the toxicity resistance of AB5 alloy

and its hydride is generally achieved through surface modification methods, which (i) provide surface catalytic activity for H2 dissociation/recombination and/or (ii) introduce catalytic active centers to protect the surface of the alloy, with the active center replacing the alloy and reacting with impurities [97]. The most effective way to form new catalytic active centers on the surface of MH is to introduce platinum group elements. At this time, mechanical alloying is a good introduction method [98].

KD Modibane et al. [99] introduced Pd into AB5 alloys by mechanical alloying combined with conventional electroless plating technology, with the composition being [*La*, *Ce*, *Pr*, *Nd*] [*Ni*, *Co*, *Al*, *Mn*]5, and studied the H2 absorption performance of Pd on the alloy and the impact of poisoning tolerance. The results show that the alloy with 1 wt.% Pd has the best H2 absorption kinetic performance.
