Xiao Han

Ceramic aerogels are acclaimed as ideal materials for extreme environments due to their ultrahigh porosity, low density, and exceptional thermal stability. However, the practical application of traditional ceramic aerogels is constrained by their inherent mechanical brittleness. Herein, a strategy is proposed to customize mechanically tunable aerogels by armoring ceramic nanounits with pyrolytic carbon (PyC). The PyC encapsulating layers with various thicknesses are transformed into ductile tights or rigid armors, facilitating the mechanical customization of BN@PyC aerogel from superelasticity to rigidity across scales. Interestingly, the PyC armor imparts unique versatility to the aerogel, including flame retardancy, elastic response conductivity, and thermal conductivity. Furthermore, owing to the thermal stability of the PyC armor, the BN@PyC aerogel maintains its mechanical integrity even after high‐temperature thermal treatment, and exhibits an unexpected resistance to butane torch ablation. Integrating mechanical stability, high‐temperature resistance, and multifunctionality, BN@PyC aerogels offer new possibilities for scalable applications in extreme environments. This facile strategy of armoring brittle ceramic aerogels with PyC provides a novel reference for customizing the mechanical properties of multifunctional aerogels.

The development of mechanically robust and electrochemically active high-performance electrodes is essential for the electrocatalytic process, thus reducing the energy input and achieving excellent environmental tolerance. In this case, high-entropy alloys, as a rising star with excellent mechanical stability and electrochemical performance, can be applied as both structural and functional electrodes in the field of conversion and storage. Herein, a high-entropy alloy electrode with hierarchically porous structure (PHEA) was designed and fabricated via the selective etching of a eutectic two-phase microstructure. Compared with commercial nickel foam (NF) as an electrocatalyst substrate, PHEA possessed better mechanical robustness, larger specific surface area, more favorable electrocatalytic activity and long-term stability. Subsequently, a surface modification strategy was proposed to decorate the PHEA substrate via a facile noble-metal-doped-layered double hydroxide (LDH) regulating route. Electrochemical measurements showed that the PHEA electrode modified with trace-noble-metal-doped-LDH exhibited excellent catalytic activity and stability, with overpotentials of 21 and 227 mV at a current density of 10 mA cm⁻² for the hydrogen evolution (HER) and oxygen evolution reaction (OER), respectively. The X-ray photoelectron spectra and in situ FT-IR spectra indicated that the successful doping of Pt contributed to the enhancement in the HER performance, and the in situ Raman spectra revealed the structural transformation on the catalyst surface during the OER process. Surprisingly, long-term stability at an ultrahigh industrial-level current density (∼1 A cm⁻²) was observed when employing the bifunctional LDH@PHEA electrode assembly in an overall water splitting device. This work explored the advantages and application of PHEA as a versatile electrocatalyst substrate, thus providing new insights and approaches for designing and constructing robust porous electrodes via surface modification towards efficient hydrogen generation.

The electrocatalytic urea oxidation reaction (UOR) can be utilized as an alternative anodic reaction for water electrolysis to provide more economic electrons and high-efficiency H₂ production.

High entropy alloys (HEAs) are promising as multifunctional electrocatalysts owing to their inherent compositional and structural complexity and thus the multiple active sites for different reactions. Herein, a binder-free bifunctional porous HEA electrode has been designed and fabricated by selectively etching eutectic dual-phase microstructures. The AlCrFeCoNiW HEA consisting of FCC and ordered BCC phases was dealloyed with the aluminum-enriched BCC phase being removed effectively to construct a three-dimensional porous architecture. The porous HEA electrode exhibits excellent hydrogen evolution reaction activity (overpotential of 101 mV at a current density of 10 mA cm⁻²) and oxygen evolution reaction activity (overpotential of 270 mV at a current density of 50 mA cm⁻²), along with outstanding stability under industrial conditions. The in situ electrochemical infrared spectra illustrate that the great electrocatalytic performance in alkaline electrolyte may be closely related to the enhanced interactions between the electrode surface and adsorbed water molecules. First-principles calculations based on density functional theory reveal an improvement in the intrinsic catalytic activity after the dealloying process. This work combines the concept of HEA with multiple active sites for catalysis and selective etching tuned by the eutectic microstructure, paving a new way for designing low-cost self-supporting electrodes for future sustainable energy applications.

Background: Cellulose Nanofibrils (CNFs) are natural nanomaterials with nanometer dimensions. Compared with ordinary cellulose, CNFs own good mechanical properties, large specific surface areas, high Young's modulus, strong hydrophilicity and other distinguishing characteristics, which make them widely used in many fields. This review aims to introduce the preparation of CNFs-based hydrogels and their recent biomedical application advances.Methods: By searching the recent literatures, we have summarized the preparation methods of CNFs, including mechanical methods and chemical mechanical methods, and also introduced the fabrication methods of CNFs-based hydrogels, including CNFs cross-linked with metal ion and with polymers. In addition, we have summarized the biomedical applications of CNFs-based hydrogels, including scaffold materials and wound dressings.Results: CNFs-based hydrogels are new types of materials that are non-toxic and display a certain mechanical strength. In the tissue scaffold application, they can provide a micro-environment for the damaged tissue to repair and regenerate it. In wound dressing applications, it can fit the wound surface and protect the wound from the external environment, thereby effectively promoting the healing of skin tissue.Conclusion: By summarizing the preparation and application of CNFs-based hydrogels, we have analyzed and forecasted their development trends. At present, the research of CNFs-based hydrogels is still in the laboratory stage. It needs further exploration to be applied in practice. The development of medical hydrogels with high mechanical properties and biocompatibility still poses significant challenges.