Hollow Mesoporous Aluminosilica Spheres with Perpendicular Pore Channels as Catalytic Nanoreactors

The design and synthesis of hollow/yolk-shell mesoporous structures with catalytically active ordered mesoporous shells can infuse new vitality into the applications of these attractive structures. In this study, we report that hollow/yolk-shell structures with catalytically active ordered mesoporous aluminosilica shells can be easily prepared by using silica spheres as the silica precursors. By simply treating with a hot alkaline solution in the presence of sodium aluminate (NaAlO₂) and cetyltrimethylammonium bromide (CTAB), solid silica spheres can be directly converted into high-quality hollow mesoporous aluminosilica spheres with perpendicular pore channels. On the basis of the proposed formation mechanism of etching followed by co-assembly, the synthesis strategy developed in this work can be extended as a general strategy to prepare ordered mesoporous yolk-shell structures with diverse compositions and morphologies simply by replacing solid silica spheres with silica-coated nanocomposites. The reduction of 4-nitrophenol with yolk-shell structured Au@ordered mesoporous aluminosilica as the catalyst has clearly demonstrated that the highly permeable perpendicular pore channels of mesoporous aluminosilica can effectively prevent the catalytically active yolk from aggregating. Furthermore, with accessible acidity, the yolk-shell structured ordered mesoporous aluminosilica spheres containing Pd yolk exhibit high catalytic activity and recyclability in a one-pot two-step synthesis involving an acid catalysis and subsequent catalytic hydrogenation for desired benzimidazole derivative, which makes the proposed hollow ordered aluminosilica spheres a versatile and practicable scaffold for advanced catalytic nanoreactor systems

Thermally Conductive Boron Nitride Nanosheet Composite Paper as a Flexible Printed Circuit Board

The development of portable and wearable electronic devices has substantially increased the demand for printed circuit boards with high thermal conductivity, optimal mechanical flexibility, electrical insulativity, and minimal high-frequency transmission loss. Herein, we demonstrate the fabrication of a thermally conductive, flexible composite paper, for electronic and microwave devices, based on hexagonal boron nitride nanosheets, poly­(vinyl alcohol) (PVA), and fiberglass mesh (FGM). The prepared composite paper exhibits in-plane thermal conductivity of 22.51 W/(m·K), and the FGM induced high mechanical strength of 27.92 MPa. The transmission loss, of the grounded coplanar waveguide lines, was 0.10 dB/mm at 7.0 GHz, and shows negligible variation while bending, indicating the high flexibility of the circuit board. These results demonstrate potential application of BN-based composite paper in flexible electronic devices

Constructing robust 3D ionomer networks in the catalyst layer to achieve stable water electrolysis for green hydrogen production

The widespread application of proton exchange membrane water electrolyzers (PEMWEs) is hampered by insufficient lifetime caused by degradation of the anode catalyst layer (ACL). Here, an important degradation mechanism has been identified, attributed to poor mechanical stability causing the mass transfer channels to be blocked by ionomers under operating conditions. By using liquid-phase atomic force microscopy, we directly observed that the ionomers were randomly distributed (RD) in the ACL, which occupied the mass transfer channels due to swelling, creeping, and migration properties. Interestingly, we found that alternating treatments of the ACL in different water/temperature environments resulted in forming three-dimensional ionomer networks (3D INs) in the ACL, which increased the mechanical strength of microstructures by 3 times. Benefitting from the efficient and stable mass transfer channels, the lifetime was improved by 19 times. A low degradation rate of approximately 3.0 μV/h at 80 °C and a high current density of 2.0 A/cm2 was achieved on a 50 cm2 electrolyzer. These data demonstrated a forecasted lifetime of 80 000 h, approaching the 2026 DOE lifetime target. This work emphasizes the importance of the mechanical stability of the ACL and offers a general strategy for designing and developing a durable PEMWE.</p