Biaxial Stretching Array Based on High-Energy-Efficient MXene-Based Al-Ion Micro-supercapacitor Island and Editable Stretchable Bridge

Employment of multivalent charge carriers with higher charge density to replace frequently used univalent ones can effectively increase the areal capacitance of micro-supercapacitors utilizing few-layered MXene self-assembled electrodes. However, their larger charge density and ionic size usually lead to a sluggish extraction/insertion dynamic between MXene interlayers with limited free space, greatly offsetting the benefits. Herein, we show how to facilitate de-/intercalation of high-valence charge carriers (Al3+) by using polypyrrole-coated bacterial cellulose (BC@PPy) nanospacers to expand MXene interlayer space. Together with the longitudinal electron transport path between interlayers synchronously constructed by the conductive PPy shell, a significant 496% areal capacitance enhancement (232.79 mF cm–2) is realized in the fabricated symmetric Al3+-ion micro-supercapacitors (AMSCs) with the obtained MXene/BC@PPy hybrid film electrodes employing polyacrylamide/1 M AlCl3·6H2O hydrogel electrolyte relative to the cell with pure MXene film electrodes (39.02 mF cm–2). Further benefiting from a high output voltage of 1.2 V, the AMSCs acquire an areal energy density up to 45.3 μW h cm–2. As a device demonstration, we further fabricate a biaxially stretchable AMSC array, simulate its spatial strain distribution during biaxial stretching, and characterize its electrochemical and mechanical properties up to an extreme areal strain of 300%. The proposed rational fabrication paradigm achieves a new level of combined energy density, stretch performance, and architectural simplicity, which presents a route toward a commercially viable stretchable micro energy-storage system with high energy efficiencies

Low-Cost, Acid/Alkaline-Resistant, and Fluorine-Free Superhydrophobic Fabric Coating from Onionlike Carbon Microspheres Converted from Waste Polyethylene Terephthalate

Onionlike carbon microspheres composed of many nanoflakes have been prepared by pyrolyzing waste polyethylene terephthalate in supercritical carbon dioxide at 650 °C for 3 h followed by subsequent vacuum annealing at 1500 °C for 0.5 h. The obtained onionlike carbon microspheres have very high surface roughness and exhibit unique hydrophobic properties. Considering their structural similarities with a lotus leaf, we further developed a low-cost, acid/alkaline-resistant, and fluorine-free superhydrophobic coating strategy on fabrics by employing the onionlike carbon microspheres and polydimethylsiloxane as raw materials. This provides a novel technique to convert waste polyethylene terephthalate to valuable carbon materials. At the same time, we demonstrate a novel application direction of carbon materials by taking advantage of their unique structural properties. The combination of recycling waste solid materials as carbon feedstock for valuable carbon material production, with the generation of highly value-added products such as superhydrophobic fabrics, may provide a feasible solution for sustainable solid waste treatment

Fabrication of Orientation-Tunable Si Nanowires on Silicon Pyramids with Omnidirectional Light Absorption

In this work, the different orientation of SiNWs on Si pyramids by a two step MACE method have been fabricated. By tuning the structure of Ag catalyst film and controlling the concentration of H₂O₂ or the etching temperature, the tunability of the orientation of SiNWs from <111> to <100> on Si pyramids was realized. Si structures composed of Si pyramids and SiNWs exhibit better omnidirectional light-trapping ability by multiple reflections. Si structures with structural tunability and enhanced light harvesting performance will find a wide variety of significant applications in solar cells, photodetectors, and optoelectronic devices

One for Two: Conversion of Waste Chicken Feathers to Carbon Microspheres and (NH₄)HCO₃

Pyrolysis of 1 g of waste chicken feathers (quills and barbs) in supercritical carbon dioxide (sc-CO₂) system at 600 °C for 3 h leads to the formation of 0.25 g well-shaped carbon microspheres with diameters of 1–5 μm and 0.26 g ammonium bicarbonate ((NH₄)­HCO₃). The products were characterized by powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman spectroscopic, FT-IR spectrum, X-ray electron spectroscopy (XPS), and N₂ adsorption/desorption measurements. The obtained carbon microspheres displayed great superhydrophobicity as fabric coatings materials, with the water contact angle of up to 165.2 ± 2.5°. The strategy is simple, efficient, does not require any toxic chemicals or catalysts, and generates two valuable materials at the same time. Moreover, other nitrogen-containing materials (such as nylon and amino acids) can also be converted to carbon microspheres and (NH₄)­HCO₃ in the sc-CO₂ system. This provides a simple strategy to extract the nitrogen content from natural and man-made waste materials and generate (NH₄)­HCO₃ as fertilizer