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 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 systems. Titanium (Ti) as an active element, shows 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 has the potential to guide the design of high-efficient catalysts and provide embedded guidance for future development and application of Mg-based materials in hydrogen storage system.

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.

This study focuses on enhancing the photocatalytic performance of Ti(HPO₄)₂ for H₂O₂ synthesis. Ti(HPO₄)₂, an intercalated structure photocatalyst with suitable band gap energy, has great potential in photocatalytic applications. However, its performance in H₂O₂ photosynthesis needs improvement in oxygen reduction kinetics and electron lifetime. We employed oxygen vacancy engineering to modulate the local oxygen environment of Ti(HPO₄)₂. This process reconstructs the Ti³⁺-O_v-P structures by leveraging push-pull electronic effects to increase the electron density at Ti⁴⁺ sites, thereby enhancing O₂ adsorption and activation. Moreover, we constructed an S-scheme heterojunction using WO₃ as a complementary oxidative cocatalyst. This heterojunction effectively suppressed carrier recombination and preserved the intrinsic redox abilities of each component. The optimized WO₃/TPO_v showed remarkable performance in a pure H₂O/O₂ system without sacrificial agents. It exhibited a 15-fold activity enhancement over pristine TPO and achieved an SCC efficiency of 0.75%. Our work offers a novel strategy of defect and heterojunction engineering for optimizing carrier lifetime and surface reactivity in photocatalytic systems.

Synergizing photocatalysis with external fields offers a promising strategy to surpass limitations of single catalytic systems, yet designing catalysts that works in multi-field remains challenging. In this work, we explore catalysts that improves photocatalysis in solution plasma to significantly enhance H₂O₂ production. We focus on bronze TiO₂ and tune its crystallinity through an adjusted sodium titanate precursor route. In particular, the regular and wide tunnel structure of Na₂Ti₆O₁₃ precursor results in bronze TiO₂ with exceptional crystallinity. Upon introducing highly crystalline bronze TiO₂ nanobelts into solution plasma, we effectively suppress the photocatalytic decomposition of H₂O₂ in plasma field, reducing the decomposition rate by 70% compared to commercial P25 TiO₂ photocatalysts. Further carbon coating results in H₂O₂ concentrations up to 3.7 mmol/L, which is 1-3 orders of magnitude higher than most photocatalytic systems. Our work elucidates the potential photocatalytic effects within solution plasma and achieves synergy between photocatalysis and solution plasma.

Environmental pollution and energy shortage pose major challenges to sustainable development. Photocatalytic technology using solar energy for pollutant degradation and resource conversion is a promising solution. However, conventional photocatalysts and reactors have limitations such as narrow light absorption, fast charge recombination, difficulty in recovery and continuous operation. The characteristics of surface reactions in photocatalytic technology also put forward higher requirements for light field design. 3D printing (Additive manufacturing) provides an innovative strategy to solve these problems. It enables the controllable design of photocatalyst microstructures in terms of pore size, morphology and surface characteristics through high-precision and customizable manufacturing methods, thus significantly improving the specific surface area, enhancing the light capture ability and carrier separation efficiency. At the same time, 3D printing technology can also manufacture photocatalytic reactors with complex flow channel structures, multi-scale mass transfer interfaces and integrated functional units, which can effectively optimize the distribution and transmission of reactants and light, realize the collaborative enhancement of reaction-mass transfer-illumination, and support the system integration of multifunctional modules. This review systematically summarizes the technical progress, core challenges and application potential of this cross-field, and provides reference for the subsequent research on 3D printing innovation of photocatalytic materials and devices.