Tong Liu

Efficient hydrogen separation and purification technology plays a crucial role in the hydrogen energy industry. VB-group alloy membranes have demonstrated favorable hydrogen permeability, but their hydrogen embrittlement resistance remains generally insufficient. This work designed Nb₃₅Hf₃₀Co₁₅Ni_20-xMo_x high-entropy alloy (HEA) membranes with regulated Ni and Mo contents. The influences of HEA compositions on microstructures, hydrogen permeability and hydrogen embrittlement resistance were systematically analyzed. On the one hand, the doping of Mo increased the volume and proportion of BCC-Nb phase, thus promoting hydrogen permeation; on the other hand, the hydrogen solubility was reduced, thus enhancing the hydrogen embrittlement resistance. The lattice distortion effect, sluggish diffusion effect and optimized Mo content collectively enhanced the comprehensive performance of Nb₃₅Hf₃₀Co₁₅Ni_12.5Mo_7.5, achieving a hydrogen permeability (Φ) of 2.68 × 10⁻⁸ mol H₂ m⁻¹·s⁻¹·Pa^−0.5 at 673 K and exhibiting excellent hydrogen embrittlement resistance, showing no hydrogen-induced fractures even at room temperature. This quantitatively demonstrates its excellent performance, which represents a certain breakthrough compared to related studies. The novel Nb₃₅Hf₃₀Co₁₅Ni_20-xMo_x HEA membranes offer excellent hydrogen permeability and improved hydrogen embrittlement resistance, thereby highlighting the potential for future hydrogen purification applications.

Nanoconfinement and single‐atom catalysis are effective strategies for improving the hydrogen storage performance of Mg. However, achieving high loading nanoconfinement Mg and introducing multiple metal single atoms catalysts simultaneously is extremely challenging. This work developed a novel metal cation doping – thermal decomposition strategy to successfully prepare Mg‐SAs@C nanocomposites with multiple metal single atoms (SAs) embedded in a MOF‐derived‐nitrogen‐doped carbon scaffold. The Mg‐(NiCoFeTi‐SAs)@C nanocomposite has fine Mg nanoparticles of 7.4 nm and a high loading rate of 72.4%. Surprisingly, Mg‐(NiCoFeTi‐SAs)@C begins to dehydrogenate at room‐temperature with a saturation capacity of 5.3 wt.%. In particular, the hydrogen release kinetics and thermodynamic performance are significantly improved (Ea _(des) = 48.5 kJ mol ⁻¹ H ₂ , ΔH _des = 59.6 kJ mol ⁻¹ H ₂ ). Attributed to the synergistic effect between multiple single atoms and N, as well as the carbon scaffold, the electron transfer efficiency is increased, resulting in a significantly higher charge transfer amount for Mg‐(NiCoFeTi‐SAs)@C (1.88 eV) compared to Mg‐(Ni‐SAs)@C (0.06 eV) with only one single‐atom added. This work has opened a new path for introducing multiple single‐atom catalysts into Mg‐based materials, and also provided new insights into exploring the catalytic mechanism of multiple metal single‐atom catalysts.

The flexible manipulation of the position and type of metal cations in spinel ferrites gives the possibility of tuning its dielectric and magnetic properties, thus opening up broad design space for broadband and low‐frequency absorption. However, there are still challenges in how to ensure that metal cations of diverse designs can be effectively introduced into the ferrite lattice to form homogeneous entropy‐stable compounds, and further engender stable ferrite compounds with special multi‐interface and hollow micro‐nano structures to achieve lightweight and efficient performance. In this paper, the opened‐hollow multi‐shell high‐entropy (FeCoNiZnMg)Fe ₂ O ₄ @C microspheres with a controllable carbon‐coated triple‐shell and entropy‐stable ferrite composition are constructed. The designed hollow triple‐shell structure enhances the magnetic interactions between the shells and regulates the magnetic domain structures and effective fields. The (FeCoNiZnMg)Fe ₂ O ₄ @C microspheres achieve an incredibly high absorption strengths (−60.5 dB) and wide effective absorption (9.3 GHz). Meanwhile, the high entropy effect effectively adjusts the anisotropic magnetic field size, significantly improving the low‐frequency absorption of 4–8 GH band, far exceeding the performance of ferrite@C materials without forming a high‐entropy phase. This unique hollow multi‐shell ferrite@C composite based on high entropy strategy offers exciting prospects for rational composition and accurate structure construction for multi‐interface polarization and lightweight design.

A reasonable construction of hollow structures to obtain high‐performance absorbers is widely studied, but it is still a challenge to select suitable materials to improve the low‐frequency attenuation performance. Here, the Fe ₃ O ₄ @C@NiO nanoprisms with unique tip shapes, asymmetric multi‐path hollow cavity, and core–shell heteroepitaxy structure are designed and synthesized based on anisotropy and intrinsic physical characteristics. Impressively, by changing the load of NiO, the composites achieve strong absorption, broadband, low‐frequency absorption: the reflection loss of −55.8 dB and the absorption bandwidth of 9.9 GHz covers both low and high frequency (2.9–6.1 and 11.3–18 GHz). The constructed anisotropic hollow and heterointerface nanoprisms can optimize impedance matching for low‐frequency absorption (3.8–7.9 GHz) almost completely covering the 5G band. Especially, the influence of hollow path on the interface polarization and ferromagnetic coupling behavior is revealed through the simulation of electric and magnetic field distribution using the High‐Frequency Structure Simulator (HFSS). In addition, HFSS simulation shows that the Radar Cross‐Sectional (RCS) value of the absorber at any angle is <−10 dB m ² , which meets the complex requirements in practical application. This research paves a new way for the development of efficient low‐frequency absorbers based on composition and structure design.

The construction of stable and efficient nanocomposites with low addition and light weight has always been the goal pursued in the field of electromagnetic wave (EMW) absorption. In this study, the Co@CNTs nanocomposites with Co nanoparticles (13 nm) nanoconfined in the carbon nanotube (CNT) are successfully synthesized by a simple hydrothermal method and phenolic assisted pyrolysis method. The degree of graphitization of CNTs and the microstructure of Co nanoparticles can be effectively regulated by controlling the calcination temperature. The sample calcined at 700 °C can obtain excellent absorption performance at a low filling capacity of 10 wt.%: the minimum reflection loss (RL) is −41.2 dB and the effective absorption bandwidth (EAB) reaches a maximum width of 14.2 GHz. When the sample thickness is only 2.2 mm, the EAB of <−20 dB reaches 8.3 GHz, which is the maximum EAB of most current Co‐based absorbers. In particular, the polarization and ferromagnetic coupling behaviors are elucidated in depth with the aid of electromagnetic field simulations using the High‐Frequency Structure Simulator (HFSS). This work provides a new nanoconfinement strategy for constructing the Co@CNTs nanocomposites as lightweight and ultra‐broadband absorbing materials for EMW protection and EMW pollution control.

The synergies of nanoconfinement and catalysis is an effective strategy to improve the kinetic and thermodynamic properties of Mg‐based materials. However, obtaining Mg‐based materials with high loading, anti‐aggregation, and containing nanocatalysts to achieve dehydrogenation at room temperature remains a huge challenge. Herein, a novel and universal preparation strategy for Mg‐Co@C nanocomposites with 9.5 nm Mg nanoparticles and 9.4 nm Co nanocatalysts embedded in carbon scaffold is reported. The 9.3 nm MgBu₂ nanosheets precipitated by solvent displacement are encapsulated in ZIF‐67 to prepare MgBu₂@ZIF‐67 precursors, then removing excess MgBu₂ on the precursor surface and pyrolysis to obtain Mg‐Co@C. It is worth noting that the Mg loading rate of Mg‐Co@C is as high as rare 69.7%. Excitingly, the Mg‐Co@C begins to dehydrogenate at room temperature with saturate capacity of 5.1 wt.%. Meanwhile, its dehydrogenation activation energy (Ea_{(des) =} 68.8 kJ mol⁻¹) and enthalpy (ΔH_(des) = 61.6 kJ mol⁻¹) significantly decrease compared to bulk Mg. First principles calculations indicate that the hydrogen adsorption energy on the Mg₂CoH₅ surface is only −0.681 eV. This work provides a universally applicable novel method for the preparation of nanoscale Mg‐based materials with various nanocatalysts added, and provides new ideas for Mg‐based materials to achieve room temperature hydrogen storage.