Hollow-structured materials exhibit breakthrough potential in energy storage and conversion, leveraging unique advantages including high specific surface area, controllable cavity architecture, and short-range mass transfer pathways, alongside tunable functional properties. This review synthesizes recent progress, emphasizing the constitutive relationships governing material synthesis, structural engineering, and resultant performance. Key synthesis strategies including encompassing hard-templating, soft-templating, and template-free approaches are delineated with respect to their mechanisms and characteristics. Subsequently, cutting-edge applications in energy storage systems (e.g., lithium-ion batteries, supercapacitors), conversion systems (e.g., photoelectrocatalysis) and the application of partial in-situ testing technology for exploring the reaction mechanism are highlighted. The review concludes by outlining critical challenges and opportunities pertaining to scalable fabrication, structural stability, and device integration, providing a roadmap for the precise design and performance optimization of these materials.

Magnesium hydride (MgH₂) as a solid-state hydrogen storage material has obtained intense attention in extensive research because of its high hydrogen-storage capacity, excellent reversibility, and a relatively low cost. However, two primary obstacles of slow kinetics during hydrogenation/dehydrogenation process and high thermodynamic stability of Mg-H bond hinders the large-scale application of MgH₂. Therefore, developing high-efficiency catalysts is necessary for hydrogen storage system. Titanium (Ti) as an active element has the promising in enhancing hydrogen storage activity and has been reported extensively. Herein, this review summarized the synthesis approaches, testing technology, and hydrogen storage performance of various Ti-based additives in detail. The structure-activity relationship of Ti-based materials was researched by combining experiment and DFT simulations. In particular, the focus is on the investigation of synthesis, characterization and reaction mechanism of various Ti-based additives. The real active sites and different reaction mechanisms during MgH₂ hydrogen storage system are discussed. Finally, a summary and outlook were also presented. This review may have potential in designing high-efficient catalysts and providing embedded guidance for future development and application of Mg-based materials during the system of hydrogen storage.