Improving the hydrogen storage performance of MgH₂ by compositing with Ce/N–codoped TiO₂

MgH₂ shows promise for solid-state hydrogen storage because of its high gravimetric capacity (7.6%) and ecofriendliness but cannot be easily commercialized because of its sluggish dehydrogenation/rehydrogenation kinetics and high thermodynamic stability. Herein, Ce/N–codoped TiO₂ (CN-T) synthesized using a solvothermal/calcination method was composited with MgH₂ to enhance its hydrogen storage performance. The composite with a CN-T loading of 7 wt% started releasing H₂ at 187.2 ℃ and released 6.45 wt.% H₂ in 180 s at 301 ℃, which corresponded to nearly complete dehydrogenation. The residue could be rapidly rehydrogenated, with hydrogen contents of 3.24 and 5.45 wt% achieved in 1 min at 100 ℃/20 bar H₂ and 5 min at 200 ℃/20 bar H₂, respectively. This performance enhancement was attributed to the combined effects of doped N, multivalent Ti, and Ce. The doped N weakened Mg–H bonds via charge transfer and modified the electronic state density of MgH₂. Ti catalyzed H₂ dissociation/recombination through dynamic valence cycling and D-electron injection, and the introduction of Ce³⁺ created O vacancies, which lowered the electron density of Mg–H bonds, generated strain fields for hydrogen release, provided diffusion pathways, and introduced bandgap states to strengthen electron–hydrogen coupling. Thus, this study paves the way for the commercialization of MgH₂ as a green high-capacity hydrogen carrier for diverse applications.