• Multicomponent and high-entropy catalysts significantly enhance the hydrogen storage performance of MgH2 by improving kinetics and reducing operating temperatures.
• The 'hydrogen pump' effect of Mg2Ni(Cu)/Mg2Ni(Cu)H4 and the 'hydrogen gateway' effect of Co3Fe7 are key catalytic mechanisms in high-entropy alloy-doped MgH2 systems.
• Catalyst doping destabilizes Mg–H bonds, provides active sites for hydrogen dissociation, and facilitates hydrogen absorption and diffusion, addressing major limitations of MgH2.
• Future research directions include optimizing multicomponent catalyst design and understanding structure–property relationships to further advance Mg-based hydrogen storage technologies.