Cheng Zhang

Buildings account for nearly one-third of global energy consumption, creating an urgent demand for sustainable, low-conductivity insulation derived from renewable feedstocks. Soft polymeric microtubes are attractive candidates because their hollow, low-density architecture suppresses both conductive and convective heat transfer, yet their fabrication from natural polymers has long been hindered by jet instability, low throughput, and difficulty in controlling wall structures. Here, we report a sheath-assisted triaxial electrospinning strategy that overcomes these limitations and enables the high-throughput, eco-friendly fabrication of ethyl cellulose (EC) microtubes with independently tunable diameter, wall thickness, and porosity. An inner oil core, a middle EC solution, and an outer ethanol sheath are co-extruded through concentric needles; the ethanol sheath stabilizes the multilayer jet at flow rates up to 30 mL h–1 per needle—an order of magnitude higher than typical electrospinning throughputs—while preserving structural integrity. By varying the core oil flow rate and viscosity, tube diameter and wall thickness are continuously tuned from 3.0 ± 1.2 to 19.2 ± 7.0 μm and from 1940 ± 300 to 120 ± 30 nm, respectively, with low-viscosity oils favoring the smallest, most uniform tubes. Increasing the EC solution flow rate from 5 to 30 mL h–1 transforms the wall from a dense to a highly porous architecture through accelerated phase separation and solvent evaporation. The resulting hollow, porous EC microtubes deliver low thermal conductivities of 0.130 ± 0.007 W m–1 K–1 (radial) and 0.060 ± 0.003 W m–1 K–1 (axial), reduce surface temperatures by more than 30 °C against a 70 °C heat source, and visibly protect heat-sensitive flowers from thermal damage. Together, these results establish a scalable, solvent-lean platform for converting a renewable polysaccharide into energy-efficient insulation materials for sustainable building applications.

This study demonstrates an EC-assisted SF electrospinning method with a green ethanol post-processing step. Overcoming pure SF limitations, it enables efficient synthesis of SF nanofibers to broaden SF-based material applications.

Ethyl cellulose (EC), a low-cost, biocompatible, renewable, and recyclable polysaccharide, exhibits environmentally friendly properties that make it ideal for industrial and biomedical applications. Hollow tubular structures offer expanded inner and outer surface areas, enhancing efficiency in surface-dependent processes, while tunable diameters enable precise control over transport properties. Herein, we introduce a triaxial electrospinning approach utilizing an oil-phase core, EC polymer middle layer, and ethanol sheath flow to stabilize the jet, enabling the fabrication of soft EC microtubes with adjustable diameter (3.0±1.2 to 19.2±7.0 μm), wall thickness (1940±300 to 120±30 nm), and porosity. The sheath-assisted method achieves high-throughput production at 30 mL/h per needle—far exceeding literature reports—while maintaining structural integrity. Tube dimensions are finely tuned by varying the core oil flow rate, with oil viscosity showing a positive correlation to diameter; low-viscosity oils yield the smallest tubes. Increasing the EC solution flow rate promotes porous wall formation via accelerated phase separation and solvent evaporation. These hollow, porous structures significantly improve thermal insulation, with radial and axial conductivities of 0.130±0.007 and 0.060±0.003 W/(m·K), respectively, effectively mitigating heat transfer up to 70 °C. Thus, the EC microtubes demonstrate strong potential as sustainable, energy-efficient insulation materials for building applications.

Ethyl cellulose (EC) is a biocompatible, renewable, and recyclable material with diverse sources, making it an attractive candidate for industrial applications. Electrospinning has gained significant attention for the production of EC fibers. However, conventional electrospinning methods face challenges such as bead formation, low yield, and the absence of porous internal structures, limiting both the functional performance and scalability. This study presents an optimized approach for producing EC fibers by using a gravity-driven ultrahigh-speed electrospinning (GUHS-ES) system. This system leverages gravity to reshape the Taylor cone morphology during electrospinning, enhancing stability and dramatically increasing throughput. As flow rates increase, the Taylor cone contracts inward, while the tip structure expands and stabilizes, reaching maximum size at ultrahigh flow rates (100-150 mL/h). This unique Taylor cone structure enables a fiber production rate of 24.5 g/h, hundreds of times greater than conventional electrospinning techniques. Another advantage of the GUHS-ES system is its ability to achieve both high diameter uniformity and adjustable porosity. At ultrahigh flow rates, the pore sizes of the EC fibers reached 321 nm. The highly porous structure of EC fibers exhibited an absorption capacity of 56.6 to 110.7 times their weight, exceeding most previously reported oil-absorbing materials and demonstrating high efficacy for rapid waste oil absorption. This green, efficient technology represents a promising advancement for the large-scale production and application of natural polymer fibers with broad implications for sustainable industrial processes.

Carbon-based nanofibers are critical materials with broad applications in industries such as energy, filtration, and biomedical devices. Polyacrylonitrile (PAN) is a primary precursor for carbon nanofibers, but conventional electrospinning techniques typically operate at low production rates of 0.1-1 mL/h from a single spinneret, limiting scalability. In this study, we introduce a novel liquid-assisted ultrahigh-speed electrospinning (LAUHS-ES) technique that achieved actual production rates over 220 times faster than conventional methods. This dramatic increase in throughput is achieved through Taylor cone stabilization using a thin layer of liquid sheath, allowing for ultrahigh-speed electrospinning without compromising the structural integrity or uniformity of the nanofibers. Comprehensive characterization, including scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), confirmed the high quality, consistency, and crystallinity of the produced nanofibers. Our results demonstrate that PAN nanofiber fabrication can be scaled up significantly while maintaining precise control over fiber morphology and performance. This advancement holds substantial promise for large-scale industrial applications, enabling more efficient and cost-effective production of carbon-based nanofibers.

Ethyl cellulose (EC) is one of the most widely used cellulose derivatives. Nevertheless, challenges such as the formation of beaded fibers, low yield, and nonporous internal structure persist in electrospinning, limiting functional improvements and industrial applications. This study invented a groundbreaking high-speed electrospinning technique through sheath liquid assistance to optimize the Taylor cone, dramatically enhancing the yield, morphology, and formation of porous structures of EC nanofibers beyond what has been seen in the literature to date. Our study emphasizes the crucial role of the sheath liquid's physical and chemical properties in controlling the morphology and diameter of EC nanofibers. It was discovered that highly polar and viscous sheath liquids led to the formation of beaded structures. Most importantly, the sheath liquid-assisted method substantially increased the ejection rate of the EC solution tens and hundreds of times compared to the current low-speed electrospinning method (0.1-1 mL/h) by refining the shape of the Taylor cone and resolving low productivity challenges in conventional nanofiber production. Meanwhile, increasing the flow rate of the EC or the sheath liquid accelerated the phase separation of EC solutions, thereby promoting the formation of porous structures in EC nanofibers. A pronounced porous structure was observed when the core EC flow rate reached 25 mL/h or the sheath chloroform flow rate reached 20 mL/h. Furthermore, our sheath liquid-assisted high-speed electrospinning technique demonstrated universal applicability to ECs with varying molecular weights. This study comprehensively addressed challenges in controlling the yield, morphology, and internal structure of EC nanofibers through sheath-solution-assisted high-speed electrospinning technology. These findings provide an innovative approach to developing next-generation electrospinning technologies to enhance the yield and properties of natural polymers for sustainability.

In this study, we explored an innovative application of heat-assisted solution electrospinning, a technique that significantly advances the control of phase separation in polystyrene (PS) fibers. Our experimental approach involved the use of direct heating and a convection air sheath applied through a coaxial needle, focusing on solvents with varying vapor pressures. This method enabled a detailed investigation into how solvent evaporation rates affect the morphology of the electrospun fibers. SEM and AFM measurements revealed that the application of direct heating and a heated air sheath offered precise control over the fiber morphology, significantly influencing both the surface and internal structure of the fibers. Additionally, we observed notable changes in fiber diameter, indicating that heat-assisted electrospinning can be effectively utilized to tailor fiber dimensions according to specific application requirements. Moreover, our research demonstrated the critical role of solvent properties, particularly vapor pressure, in determining the final characteristics of the electrospun fibers. By comparing fibers produced with different solvents, we gained insights into the complex interplay between solvent dynamics and heat application in fiber formation. The implications of these findings are far-reaching, offering new possibilities for the fabrication of nanofibers with customized properties. Furthermore, this could have profound impacts on various applications, from biomedical to environmental, where specific fiber characteristics are crucial. This study not only contributes to the understanding of phase separation in electrospinning but also opens avenues for further research on the optimization of fiber properties for diverse industrial and scientific applications.

Amid growing concerns about climate change and energy sustainability, the need to create potent catalysts for the sequestration and conversion of CO₂ to value-added chemicals is more critical than ever. This work describes the successful synthesis and profound potential of high-performance nanofiber catalysts, integrating earth-abundant iron (Fe) and cobalt (Co) as well as their alloy counterpart, FeCo, achieved through electrospinning and judicious thermal treatments. Systematic characterization using an array of advanced techniques, including SEM, TGA-DSC, ICP-MS, XRF, EDS, FTIR-ATR, XRD, and Raman spectroscopy, confirmed the integration and homogeneous distribution of Fe/Co elements in nanofibers and provided insights into their catalytic nuance. Impressively, the bimetallic FeCo nanofiber catalyst, thermally treated at 1050 °C, set a benchmark with an unparalleled CO₂ conversion rate of 46.47% at atmospheric pressure and a consistent performance over a 55 h testing period at 500 °C. Additionally, this catalyst exhibited prowess in producing high-value hydrocarbons, comprising 8.01% of total products and a significant 31.37% of C₂₊ species. Our work offers a comprehensive and layered understanding of nanofiber catalysts, delving into their transformations, compositions, and structures under different calcination temperatures. The central themes of metal-carbon interactions, the potential advantages of bimetallic synergies, and the importance of structural defects all converge to define the catalytic performance of these nanofibers. These revelations not only deepen our understanding but also set the stage for future endeavors in designing advanced nanofiber catalysts with bespoke properties tailored for specific applications.

For this work, we investigated the promotor effect (M = Na⁺, K⁺, Ce³⁺, Zn²⁺, Mn²⁺) on carbon nanosphere-encapsulated bimetallic Fe-Co core–shell catalysts for CO₂ hydrogenation, promising selectivity for converting CO₂ to light olefins. The fresh and spent catalysts were characterized using a combination of experimental techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA–DSC), and Raman spectroscopy, and our results reveal that the addition of the promotor M enhanced the formation of graphitic carbon and metal carbides in the promoted catalysts when compared with the unpromoted catalysts. The metal carbides were determined to be the active sites for the production of light olefins.