Sustainable dielectric relaxation across a broad temperature window remains a significant challenge for high-temperature electromagnetic-wave (EMW) absorption, particularly in extreme conditions where dissipation pathways are severely constrained. Herein, a porous ceramic embedded with high-entropy nanocrystals (P-HEN) was developed by leveraging the confinement effect of the SiOCN covalent network. The confined growth and effective phase separation of (FeNiCoAl)₃O₄ nanocrystals generate thermally stable dielectric-relaxation activation units within the SiOCN matrix. Furthermore, the random distribution of multi-metal cations in the nanocrystals, together with the multi-interfacial interactions between the nanocrystals and the matrix, generates strong polarization responses. Consequently, P-HEN achieves sustained dielectric relaxation and full-band effective absorption in the X-band over a wide temperature range from 25 °C to 700 °C, while also exhibiting excellent thermal insulation and ablation resistance. This work demonstrates a confinement-enabled mechanism for stabilizing dielectric-relaxation loss at elevated temperatures, providing a new strategy for designing wide-temperature-window EMW absorbers.

Searching for inexpensive, efficient and durable electrocatalysts with earth-abundant elements toward the hydrogen evolution reaction (HER) is of vital importance for the future sustainable hydrogen economy, yet still remains a formidable challenge. Herein, a facile template-engaged strategy is demonstrated for the direct in-situ growth of Ni nanoparticles and N-doped carbon nanotubes on carbon nanorod substrates, forming a hierarchically branched architecture (abbreviated as Ni@N-C NT/NRs hereafter). The elaborate construction of such unique hierarchical structure with tightly encapsulated Ni nanoparticles and open configuration endows the as-fabricated Ni@N-C NT/NRs with abundant well-dispersed active sites, enlarged surface area, reduced resistances of charge transfer and mass diffusion, and reinforced mechanical robustness. As a consequence, the optimal Ni@N-C NT/NR catalyst demonstrates superior electrocatalytic activity with relatively low overpotential of 134 mV to deliver a current density of 10 mA·cm^-2 and excellent stability for HER in 0.1 M KOH, holding a great promise for practical scalable H₂ production. More importantly, this work offers a reliable methodology for feasible fabrication of robust high-performance carbon-based hierarchical architectures for a variety of electrochemical applications.

Transition metal chalcogenides represent a class of the most promising alternative electrode materials for high-performance lithium-ion batteries (LIBs) owing to their high theoretical capacities. However, they suffer from large volume expansion, particle agglomeration, and low conductivity during charge/discharge processes, leading to unsatisfactory energy storage performance. In order to address these issues, we rationally designed three-dimensional (3D) hybrid composites consisting of ZnSe nanodots uniformly confined within a N-doped porous carbon network (ZnSe ND@N-PC) obtained via a convenient pyrolysis process. When used as anodes for LIBs, the composites exhibited outstanding electrochemical performance, with a high reversible capacity (1, 134 mA·h·g^-1 at a current density of 600 mA·g^-1 after 500 cycles) and excellent rate capability (696 and 474 mA·h·g^-1 at current densities of 6.4 and 12.8 A·g^-1, respectively). The significantly improved lithium storage performance can be attributed to the 3D architecture of the hybrid composites, which not only mitigated the internal mechanical stress induced by the volume change and formed a 3D conductive network during cycling, but also provided a large reactive area and reduced the lithium diffusion distance. The strategy reported here may open a new avenue for the design of other multifunctional composites towards high-performance energy storage devices.

Exploring lightweight microwave attenuation materials with strong and tunable wideband microwave absorption is highly desirable but remains a significant challenge. Herein, three-dimensional (3D) porous hybrid composites consisting of NiFe nanoparticles embedded within carbon nanocubes decorated on graphene oxide (GO) sheets (NiFe@C nanocubes@GO) as high-performance microwave attenuation materials have been rationally synthesized. The 3D porous hybrid composites are fabricated by a simple method, which involves one-step pyrolysis of NiFe Prussian blue analogue nanocubes in the presence of GO sheets. Benefiting from the unique structural features that exhibit good magnetic and dielectric losses as well as a proper impedance match, the resulting NiFe@C nanocubes@GO composites show excellent microwave attenuation ability. With a minimum reflection loss (RL) of–51 dB at 7.7 GHz at a thickness of 2.8 mm and maximum percentage bandwidth of 38.6% for RL < –10 dB at a thickness of 2.2 mm, the NiFe@C nanocubes@GO composites are superior to the previously reported state-of-the-art carbon-based microwave attenuation materials.