材料导报:能源(英文)最新文献

While TiFe alloy has recently attracted attention as the efficient catalyst to enhance de/hydrogenation rates of Mg/MgH₂, the difficulty of its activation characteristics has hindered further improvement of reaction kinetics. Herein, we report that the TiFe_0.92Mn_0.04Co_0.04 catalyst can overcome the abovementioned challenges. The synthesized MgH₂-30 wt% TiFe_0.92Mn_0.04Co_0.04 can release 4.5 wt% of hydrogen in 16 min at 250 °C, three times as fast as MgH₂. The activation energy of dehydrogenation was as low as 84.6 kJ mol⁻¹, which is 46.8% reduced from pure MgH₂. No clear degradation of reaction rates and hydrogen storage capacity was observed for at least 30 cycles. Structural studies reveal that TiFe_0.92Mn_0.04Co_0.04 partially decomposes to in-situ generated α-Fe particles dispersed on TiFe_0.92Mn_0.04Co_0.04. The presence of α-Fe reduces the formation of an oxide layer on TiFe_0.92Mn_0.04Co_0.04, enabling the activation processes. At the same time, the hydrogen incorporation capabilities of TiFe_0.92Mn_0.04Co_0.04 can provide more hydrogen diffusion paths, which promote hydrogen dissociation and diffusion. These discoveries demonstrate the advanced nature and importance of combining the in-situ generated α-Fe with TiFe_0.92Mn_0.04Co_0.04. It provides a new strategy for designing highly efficient and stable catalysts for Mg-based hydrogen storage materials.

Hydrogen holds the advantages of high energy density, great natural abundance and zero emission, making it suitable for large scale and long term energy storage, while its safe and efficient storage is still challenging. Among various solid state hydrogen storage materials, MgH₂ is promising for industrial applications due to its high gravimetric and volumetric hydrogen densities and the abundance of Mg on earth. However, the practical application of MgH₂ has been limited by its stable thermodynamics and slow hydrogen desorption kinetics. Nanocatalysis is considered as a promising approach for improving the hydrogen storage performance of MgH₂ and bringing it closer to the requirements of commercial applications. It is worth mentioning that the recently emerging two-dimensional material, MXene, has showcased exceptional catalytic abilities in modifying the hydrogen storage properties of MgH₂. Besides, MXene possesses a high surface area, excellent chemical/physical stability, and negatively charged terminating groups, making it an ideal support for the "nanoconfinement" of MgH₂ or highly active catalysts. Herein, we endeavor to provide a comprehensive overview of recent investigations on MXene-based catalysts and MXene supports for improving the hydrogen sorption properties of Mg/MgH₂. The mechanisms of hydrogen sorption involved in Mg-MXene based composites are highlighted with special emphases on thermodynamics, kinetics, and catalytic behaviors. The aim of this work is to provide a comprehensive and objective review of researches on the development of high-performance catalysts/supports to improve hydrogen storage performances of Mg/MgH₂ and to identify the opportunities and challenges for future applications.

Hydrogen storage alloys (HSAs) are attracting widespread interest in the nuclear industry because of the generation of stable metal hydrides after tritium absorption, thus effectively preventing the leakage of radioactive tritium. Commonly used HSAs in the hydrogen isotopes field are Zr₂M (M = Co, Ni, Fe) alloys, metallic Pd, depleted U, and ZrCo alloy. Specifically, Zr₂M (M = Co, Ni, Fe) alloys are considered promising tritium-getter materials, and metallic Pd is utilized to separate and purify hydrogen isotopes. Furthermore, depleted U and ZrCo alloy are well suited for storing and delivering hydrogen isotopes. Notably, all the aforementioned HSAs need to modulate their hydrogen storage properties for complex operating conditions. In this review, we present a comprehensive overview of the reported modification methods applied to the above alloys. Alloying is an effective amelioration method that mainly modulates the properties of HSAs by altering their local geometrical/electronic structures. Besides, microstructural modifications such as nano-sizing and nanopores have been used to increase the specific surface area and active sites of metallic Pd and ZrCo alloys for enhancing de-/hydrogenation kinetics. The combination of metallic Pd with support materials can significantly reduce the cost and enhance the pulverization resistance. Moreover, the poisoning resistance of ZrCo alloy is improved by constructing active surfaces with selective permeability. Overall, the review is constructive for better understanding the properties and mechanisms of hydrogen isotope storage alloys and provides effective guidance for future modification research.

Magnesium hydride is one of the most promising solid-state hydrogen storage materials for on-board application. Hydrogen desorption from MgH₂ is accompanied by the formation of the Mg/MgH₂ interfaces, which may play a key role in the further dehydrogenation process. In this work, first-principles calculations have been used to understand the dehydrogenation properties of the Mg(0001)/MgH₂(110) interface. It is found that the Mg(0001)/MgH₂(110) interface can weaken the Mg–H bond. The removal energies for hydrogen atoms in the interface zone are significantly lower compared to those of bulk MgH₂. In terms of H mobility, hydrogen diffusion within the interface as well as into the Mg matrix is considered. The calculated energy barriers reveal that the migration of hydrogen atoms in the interface zone is easier than that in the bulk MgH₂. Based on the hydrogen removal energies and diffusion barriers, we conclude that the formation of the Mg(0001)/MgH₂(110) interface facilitates the dehydrogenation process of magnesium hydride.

Photocatalytic and photoelectrochemical water splitting using semiconductor materials are effective approaches for converting solar energy into hydrogen fuel. In the past few years, a series of photocatalysts/photoelectrocatalysts have been developed and optimized to achieve efficient solar hydrogen production. Among various optimization strategies, the regulation of spin polarization can tailor the intrinsic optoelectronic properties for retarding charge recombination and enhancing surface reactions, thus improving the solar-to-hydrogen (STH) efficiency. This review presents recent advances in the regulation of spin polarization to enhance spin polarized-dependent solar hydrogen evolution activity. Specifically, spin polarization manipulation strategies of several typical photocatalysts/photoelectrocatalysts (e.g., metallic oxides, metallic sulfides, non-metallic semiconductors, ferroelectric materials, and chiral molecules) are described. In the end, the critical challenges and perspectives of spin polarization regulation towards future solar energy conversion are briefly provided.

Hydrogen energy has emerged as a pivotal solution to address the global energy crisis and pave the way for a cleaner, low-carbon, secure, and efficient modern energy system. A key imperative in the utilization of hydrogen energy lies in the development of high-performance hydrogen storage materials. Magnesium-based hydrogen storage materials exhibit remarkable advantages, including high hydrogen storage density, cost-effectiveness, and abundant magnesium resources, making them highly promising for the hydrogen energy sector. Nonetheless, practical applications of magnesium hydride for hydrogen storage face significant challenges, primarily due to their slow kinetics and stable thermodynamic properties. Herein, we briefly summarize the thermodynamic and kinetic properties of MgH₂, encompassing strategies such as alloying, nanoscaling, catalyst doping, and composite system construction to enhance its hydrogen storage performance. Notably, nanoscaling and catalyst doping have emerged as more effective modification strategies. The discussion focuses on the thermodynamic changes induced by nanoscaling and the kinetic enhancements resulting from catalyst doping. Particular emphasis lies in the synergistic improvement strategy of incorporating nanocatalysts with confinement materials, and we revisit typical works on the multi-strategy optimization of MgH₂. In conclusion, we conduct an analysis of outstanding challenges and issues, followed by presenting future research and development prospects for MgH₂ as hydrogen storage materials.

Photocatalytic water splitting by semiconductors is a promising technology to produce clean H₂ fuel, but the efficiency is restrained seriously by the high overpotential of the H₂-evolution reaction together with the high recombination rate of photoinduced charges. To enhance H₂ production, it is highly desirable yet challenging to explore an efficient reductive cocatalyst and place it precisely on the right sites of the photocatalyst surface to work the proton reduction reaction exclusively. Herein, the metalloid Ni_xP cocatalyst is exactly positioned on the Z-scheme Cd_0.5Zn_0.5S/NiTiO₃ (CZS/NTO) heterostructure through a facile photodeposition strategy, which renders the cocatalyst form solely at the electron-collecting locations. It is revealed that the directional transfer of photoexcited electrons from Cd_0.5Zn_0.5S to Ni_xP suppresses the quenching of charge carriers. Under visible light, the CZS/NTO hybrid loaded with the Ni_xP cocatalyst exhibits an optimal H₂ yield rate of 1103 μmol h⁻¹ (i.e., 27.57 mmol h⁻¹ g⁻¹), which is about twofold of pristine CZS/NTO and comparable to the counterpart deposited with the Pt cocatalyst. Besides, the high apparent quantum yield (AQY) of 56% is reached at 400 nm. Further, the mechanisms of the cocatalyst formation and the H₂ generation reaction are discussed in detail.