High entropy alloys (HEAs) have garnered considerable interest in catalysis owing to their unique characteristics, while transition metal oxides remain widely studied as classical catalysts. Herein, a novel core-shell FeCoNiCrCu/Fe₂O₃@C catalyst coated by a micro- and nano-scale amorphous carbon layer was prepared via a relatively facile synthesis method involving complexing multiple metal cations in organic solvents followed by calcination. Compared with MgH₂, the initial hydrogen desorption temperature of MgH₂ with the FeCoNiCrCu/Fe₂O₃@C catalyst decreases significantly from 290 ℃ to 172 ℃, and the peak temperature is reduced to 268 ℃. Furthermore, the catalyzed MgH₂ enables hydrogen absorption even at room temperature under 3 MPa. It also demonstrates excellent cyclability, maintaining over 90% of its initial capacity after 50 cycles, along with progressively enhanced dehydrogenation kinetics. The excellent hydrogen storage performance of the catalyzed MgH₂ is contributed to the synergistic interplay of catalytic components collectively, including the “hydrogen diffusion channel” effect of the in-situ generated Co₃Fe₇, the “hydrogen pump effect” exhibited by the reversible catalytic phase pair Mg₂Ni(Cu)/Mg₂Ni(Cu)H₄, as well as the multiphase interface composed of HEAs FeCoNiCrCu, Co₃Fe₇ and MgH₂. The amorphous carbon prevents particle agglomeration. This study demonstrates that the HEAs can exhibit significant catalytic effects through rational design.

Catalysis is an effective means to improve the slow kinetics of hydrogen absorption and desorption, as well as the poor cycle life of the 2LiBH₄+MgH₂ composite system. In this study, the TiVC MXene was obtained by etching TiVAlC and introduced into 2LiH + MgB₂ by ball milling. Products obtained were heated and hydrogenated to prepare the 2LiBH₄ + MgH₂ (LMBH) system, which exhibits distinguished kinetic performance and capacity retention rate. In the LMBH + 6 wt% TiVC, a 9.3 wt% hydrogen is released within 35 min at 400 ℃ as well as hydrogenation is completed within 30 min at 350 ℃, 9 MPa. Moreover, the capacity retention rate was up to 96 % after the 15^th cycle. During the heating and hydrogenation process, the TiH and V₈C₇ are generated in-situ as active products, and stably exist in the subsequent process to catalyze the hydrogen absorption-desorption reactions of the composite. The presence of TiH/LiH/V₈C₇/MgB₂ interface improves the kinetic performance of the system. Reversibility is improved by inhibiting the generation of polyborane and the aggregation during the hydrogen absorption-desorption process. The interface structure-activity relationship is first elucidated that between bimetallic MXene and 2LiBH₄ + MgH₂ composite system during hydrogen absorption-desorption processes, providing a novel viewpoint and optimization path for the modification research of 2LiBH₄ + MgH₂ composites.

Mg/MgH₂ has garnered significant attention primarily due to its abundant availability and high gravimetric density. Nevertheless, its practical implementation hindered by its high thermodynamic stability and sluggish kinetics. Fortunately, the introduction of transition metal single atom (TM SA) catalysts has emerged as an effective method to enhance the hydrogen storage properties of Mg/MgH₂. Among these catalysts, the synergistic effect of nanoconfinement and TM SAs plays a pivotal role in the hydriding/dehydriding kinetics of Mg/MgH₂. However, the effects of varying TM SAs interacting with N modified confined materials on H₂ adsorption and desorption and underlying mechanisms remain enigmatic. Leveraging DFT calculations, we investigated the potential of combining TM SA catalysts with N-modified Carbon nanomaterials (CNT) to enhance the hydrogenation/dehydrogenation of Mg/MgH₂. TM SA N-CNTs-Mg/MgH₂ heterojunction systems encompassing ten 3d/4d transition metals were designed and constructed. We systematically investigated the impact of TM SA N-CNTs on the hydrogen absorption and desorption properties of Mg/MgH₂ by examining parameters such as the electronic localization function (ELF), distorted charge density distributions, adsorption energies, dissociation energies, electronegativity, and the D-band center. Notably, the energy barriers for Mg/MgH₂ hydrogenation and dehydrogenation were significantly reduced by 0.2–0.7 eV and 1.6–2.2 eV, respectively, through the catalytic promotion of TM SA N-CNTs. Herein, a novel “electronic-ropeway” effect was proposed to elucidate the underlying mechanism responsible for enhancing the hydrogen absorption and desorption kinetics in Mg/MgH₂. Specifically, the contribution degree of TM SA N-CNTs and system electronegativity emerged as effective descriptors for predicting the reduced hydrogenation/dehydrogenation energy barriers. It is anticipated that elucidating the role of TM SA-N-CNTs will pave the way for developing innovative strategies to enhance the hydrogen absorption and desorption kinetics of Mg/MgH₂ systems, thereby providing valuable design principles for the construction of novel Mg/MgH₂ hydrogen storage materials.

Complex metal oxide catalysts greatly accelerate the hydrogen sorption rates in the magnesium hydride system. In this study, the graphene-supported Sc₂O₃/TiO₂ catalyst is synthesized by means of a simple method, and a surprisingly synergetic effect of the Sc₂O₃-TiO₂ cocatalyst on the hydrogen storage performance of MgH₂ is observed. The MgH₂-Sc₂O₃/TiO₂@Gn composite starts to release hydrogen at 140 ℃ and reaches the peak dehydrogenation temperature at 239.9 ℃. It absorbs 6.55 wt% of H₂ in 1 min and desorbs 5.71 wt% of H₂ in 10 min at 300 ℃, showing excellent hydrogen absorption and desorption performance. Furthermore, with the decrease of the grain size and changes in the structure, the activity of the catalyst is greatly improved. The low-valent titanium and scandium and oxygen vacancies formed in the process of dehydrogenation facilitate hydrogen diffusion and electron transfer, and further improve the kinetic performance of the Mg/MgH₂-Sc₂O₃/TiO₂@Gn system. This study aims to provide insights into studying complex metal oxides as catalysts to improve hydrogen storage performance, and shed light on other catalysis-related research.