Titanium‒Nickel Dual Active Sites Enabled Reversible Hydrogen Storage of Magnesium at 180 °C with Exceptional Cycle Stability

Abstract

Enhancing hydrogenation and dehydrogenation (de/hydrogenation) kinetics without compromising cycle stability is a major challenge for Mg-based hydrogen storage materials (Mg/MgH₂). The de/hydrogenation reactions of Mg/MgH₂ are one of the gas–solid reactions involving hydrogen adsorption, dissociation, diffusion, and nucleation, which often results in the catalysts being unable to simultaneously accelerate these distinct kinetic processes. Here, the Mg₂Ni@Ti─MgO catalyst with dual active sites is reported to be designed to address this issue. The stabilization of Ti²⁺ and Ti³⁺ valence states in the MgO lattice simultaneously accelerates hydrogen adsorption and dissociation. Additionally, Mg₂Ni serves as a hydrogen diffusion and nucleation center, synergistically enhancing de/hydrogenation reactions. Consequently, it enables MgH₂ to release 5.28 wt.% H₂ in 2 min at 280 °C, and achieves 1.96 wt.% H₂ of hydrogen release in 60 min at 180 °C. The Mg₂Ni@Ti─MgO catalyst exhibits remarkable chemical stability at the interfacial structure, minimizing structural and chemical degradation impact, and realizing excellent de/hydrogenation performance over 1000 cycles. These results provide a new methodology for optimizing multiple kinetic steps, attaining highly efficient and stable de/hydrogenation reactions.