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

• Ce/N–codoped TiO 2 (CN-T) is synthesized using an etching/hydrothermal method. • CN-T is compounded with MgH 2 at different loadings to afford composites. • The H 2 storage performances of these composites are evaluated using different metrics. • The optimal composite (7 wt.% CN-T) substantially outperforms pure MgH 2 . • Mechanism of CN-T-induced performance enhancement is elucidated. MgH 2 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 TiO 2 (CN-T) synthesized using a solvothermal/calcination method was composited with MgH 2 to enhance its hydrogen storage performance. The composite with a CN-T loading of 7 wt% started releasing H 2 at 187.2 °C and released 6.45 wt.% H 2 in 180 s at 301 °C, 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 °C/20 bar H 2 and 5 min at 200 °C/20 bar H 2 , 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 MgH 2 . Ti catalyzed H 2 dissociation/recombination through dynamic valence cycling and D-electron injection, and the introduction of Ce 3+ 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 MgH 2 as a green high-capacity hydrogen carrier for diverse applications.