The role of catalysts in enhancing the hydrogen storage kinetics of the Mg/MgH 2 system is pivotal. However, the exploration of efficient catalysts and the underlying principles of their design remain both a prominent focus and a significant challenge in current research. In this study, we present a bimetallic oxide of Bi 2 Ti 2 O 7 hollow sphere as a highly effective catalyst for MgH 2 . As a result, the Bi 2 Ti 2 O 7 -catalyzed Mg/MgH 2 system lowers the hydrogen desorption initiation temperature to 194.3 °C, reduces the peak desorption temperature to 245.6 °C, decreases the dehydrogenation activation energy to 82.14 kJ·mol −1 , and can absorb 5.4 wt. % of hydrogen within 60 s at 200 °C, demonstrating outstanding hydrogen ab/desorption kinetics, compared to pure MgH 2 . Additionally, it can maintain a high hydrogen capacity of 5.2 wt. %, even after 50 dehydrogenation cycles, showing good cycle stability. The characterization results show that the high-valent Bi and Ti in Bi 2 Ti 2 O 7 are reduced to their low-valent or even zero-valent metallic states during the dehydrogenation and hydrogenation process, thus establishing an in-situ multivalent and multi-element catalytic environment. Density functional theory calculations further reveal that the synergistic effects between Bi and Ti in the Bi-Ti mixed oxide facilitate the cleavage of Mg-H bonds and lower the kinetic barrier for the dissociation of hydrogen molecules, thereby substantially enhancing the kinetics of the Mg/MgH 2 system. This study presents a strategic method for developing efficient catalysts for hydrogen storage materials by harnessing the synergistic effects of metal elements.
Electrostatic dielectric capacitors are essential components in advanced electronic and electrical power systems due to their ultrafast charging/discharging speed and high power density. A major challenge, however, is how to improve their energy densities to effectuate the next-generation applications that demand miniaturization and integration. Here, we report a high-entropy stabilized Bi 2 Ti 2 O 7 -based dielectric film that exhibits an energy density as high as 182 J cm −3 with an efficiency of 78% at an electric field of 6.35 MV cm −1 . Our results reveal that regulating the atomic configurational entropy introduces favourable and stable microstructural features, including lattice distorted nano-crystalline grains and a disordered amorphous-like phase, which enhances the breakdown strength and reduces the polarization switching hysteresis, thus synergistically contributing to the energy storage performance. This high-entropy approach is expected to be widely applicable for the development of high-performance dielectrics.
Organic and inorganic ultraviolet (UV) filters possess themselves advantages, while they suffer from different limitations including photostability, penetration, and cytotoxicity. Integrating organic and inorganic UV filters in a single unit holds great potential for enhanced UV protection. Herein, the dendritic silicon dioxide microspheres (DSMs) are encapsulated with Bi2Ti2O7 nanocomposites (BTO-DSMs), an inorganic filter, and decorated with organic filters including sinapoyl malate (SM) and baicalin (BS/BTO-DSM) to enhance UV protection while significantly reducing ROS and skin permeability under UV exposure. The inorganic BTO-DSM component presents an expanded UV shield range and suppressed photocatalytic properties while preventing the organic filter SM direct contact with the epidermis and penetration behaviors. The baicalin efficiently scavenges the generated ROS from SM and reduces the transmittance of blue light. Notably, the results show that the proposed combined system significantly broadens the UV absorption region. Thus, the BS/BTO-DSM presents advanced in vitro anti-UV performance and in vivo UV protection against keratinocyte apoptosis and epidermal hyperplasia without long-term toxicity. The excellent anti-UV properties coupling with the suppressed photocatalytic capability and minimal epidermal penetration of BS/BTO-DSM make it promising for skin protection.
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