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Formation of Si Hollow Structures as Promising Anode Materials through Reduction of Silica in AlCl <sub/>3</sub> –NaCl Molten Salt
摘要： Hollow nanostructures are attractive for energy storage and conversion, drug delivery, and catalysis applications. Although these hollow nanostructures of compounds can be generated through the processes involving the well-established Kirkendall effect or ion exchange method, a similar process for the synthesis of the pure-substance one (e.g., Si) remains elusive. Inspired by the above two methods, we introduce a continuous ultrathin carbon layer on the silica nano/microstructures (St?ber spheres, diatom frustules, sphere in sphere) as the stable reaction interface. With the layer as the diffusion mediator of the reactants, silica structures are successfully reduced into their porous silicon hollow counterparts with metal Al powder in AlCl3?NaCl molten salt. The structures are composed of silicon nanocrystallites with sizes of 15?25 nm. The formation mechanism can be explained as an etching?reduction/nucleation?growth process. When used as the anode material, the silicon hollow structure from diatom frustules delivers specific capacities of 2179, 1988, 1798, 1505, 1240, and 974 mA h g?1 at 0.5, 1, 2, 4, 6, and 8 A g?1, respectively. After being prelithiated, it retains 80% of the initial capacity after 1100 cycles at 8 A g?1. This work provides a general way to synthesize versatile silicon hollow structures for high-performance lithium ion batteries due to the existence of ample silica reactants and can be extended to the synthesis of hollow structures of other materials.
关键词： carbon interface,hollow structures,silicon,molten salt,anode
更新于2025-09-23 15:21:01
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A Facile Realization Scheme for Tactile Sensing with a Structured Silver Nanowire-PDMS Composite
摘要： To mimic the sensing function of human skin, the rational design of force-sensitive materials is highly required for sensors. Here, a facile design of resistive-type tactile sensors based on a structured silver nanowire-polydimethylsiloxane composite is reported for applications in electronic skins and wearable electronics. The composite has a hollow microstructure of interconnected channels, and the inner surface of the channels is a conductive layer consisting of silver nanowires. The sensing function to external force is realized by measuring the resistance change upon deforming. The deforming causes the distance change of silver nanowires and the contact-area change of the inner surfaces. Such a unique structure promises a robust mechanical property due to the half-embedded silver nanowires which are free of peeling off, and also makes it possible to control the device sensitivity by its mechanical structure and the elastic property of the polydimethylsiloxane. The results show that the composite has steady-state responses to various pressures and stretches, even to mouth blowing, a response time of ≈90 ms, and favorable repeatability over 2000 cycles of bending/unbending. The 3D structure enables pressing, bending, pulling and torsional force sensing, and promises real-time monitoring of various human motions ranging from blood pulses to joint movements.
关键词： tactile sensing,hollow structures,Ag NWs/PDMS composite,resistive force sensors
更新于2025-09-10 09:29:36
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Preparation of TiO2 Microspheres with Tunable Pore and Chamber Size for Fast Gaseous Diffusion in Photoreduction of CO2 under Simulated Sunlight
摘要： TiO2 microsphere with tunable pore and chamber size are prepared by a simple solventhermal method and used as catalyst for the photocatalytic CO2 reduction. It is found that the hollow microsphere with relative lower surface area of 73.8 m2g-1 exhibits increased pore size of 18.1 nm and cavity structure, leading to higher CO2 diffusion coefficient of 5.40×10-5 cm2s-1 compared with the solid and yolk/shell microspheres. Therefore, the hollow microsphere possesses more accessible sites for CO2 adsorption, which finally gives rise to the enhanced CO production rate of 10.9±0.7 μmolg-1h-1 under simulated sunlight, which is respectively 1.6 and 1.4 times higher than that of solid and yolk/shell microspheres. Electron dynamic study further demonstrates that hollow microsphere shows the highest photocurrent density and the lowest charge recombination among three microspheres structure, which is attributed to the swift CO2 diffusion providing fresh CO2 molecules to rapidly scavenge the photo-generated electrons and finally leading to the excellence catalytic reduction performances. This method could be adopted as a general strategy to prepare high performance TiO2 catalysts with desirable structural qualities for the photocatalytic CO2 reduction under nature sunlight.
关键词： TiO2,CO2 reduction,Hollow structures,Photocatalysis,Mass transport
更新于2025-09-04 15:30:14