ABSTRACT
Nanoparticles suffer from aggregation and poisoning issues (e.g., oxidation) that severely hinder their long-term applications. However, current redispersion approaches, such as continuous heating in oxidizing and reducing environments, face challenges including grain growth effects induced by long heating times as well as complex procedures. Herein, we report a facile and efficient redispersion process that enables us to directly transform large aggregated particles into nanoscale materials. In this method, a piece of carbon nanofiber film was used as a heater and high treatment temperature (â¼1500-2000 K) is rapidly elevated and maintained for a very short period of time (100 ms), followed by fast quenching back to room temperature at a cooling rate of 105 K/s to inhibit sintering. With these conditions we demonstrate the redispersion of large aggregated metal oxide particles into metallic nanoparticles just â¼10 nm in size, uniformly distributed on the substrate. Furthermore, the metallic states of the nanoparticles are renewed during the heat treatment through reduction. The redispersion process removes impurities and poisoning elements, yet is able to maintain the integrity of the substrate because of the ultrashort heating pulse time. This method is also significantly faster (ca. milliseconds) compared to conventional redispersion treatments (ca. hours), providing a pragmatic strategy to redisperse degraded particles for a variety of applications.
ABSTRACT
Emerging solar desalination by interfacial evaporation shows great potential in response to global water scarcity because of its high solar-to-vapor efficiency, low environmental impact, and off-grid capability. However, solute accumulation at the heating interface has severely impacted the performance and long-term stability of current solar evaporation systems. Here, a self-regenerating solar evaporator featuring excellent antifouling properties using a rationally designed artificial channel-array in a natural wood substrate is reported. Upon solar evaporation, salt concentration gradients are formed between the millimeter-sized drilled channels (with a low salt concentration) and the microsized natural wood channels (with a high salt concentration) due to their different hydraulic conductivities. The concentration gradients allow spontaneous interchannel salt exchange through the 1-2 µm pits, leading to the dilution of salt in the microsized wood channels. The drilled channels with high hydraulic conductivities thus function as salt-rejection pathways, which can rapidly exchange the salt with the bulk solution, enabling the real-time self-regeneration of the evaporator. Compared to other salt-rejection designs, the solar evaporator exhibits the highest efficiency (≈75%) in a highly concentrated salt solution (20 wt% NaCl) under 1 sun irradiation, as well as long-term stability (over 100 h of continuous operation).
ABSTRACT
Space cooling is a predominant part of energy consumption in people's daily life. Although cooling the whole building is an effective way to provide personal comfort in hot weather, it is energy-consuming and high-cost. Personal cooling technology, being able to provide personal thermal comfort by directing local heat to the thermally regulated environment, has been regarded as one of the most promising technologies for cooling energy and cost savings. Here, we demonstrate a personal thermal regulated textile using thermally conductive and highly aligned boron nitride (BN)/poly(vinyl alcohol) (PVA) composite (denoted as a-BN/PVA) fibers to improve the thermal transport properties of textiles for personal cooling. The a-BN/PVA composite fibers are fabricated through a fast and scalable three-dimensional (3D) printing method. Uniform dispersion and high alignment of BN nanosheets (BNNSs) can be achieved during the processing of fiber fabrication, leading to a combination of high mechanical strength (355 MPa) and favorable heat dispersion. Due to the improved thermal transport property imparted by the thermally conductive and highly aligned BNNSs, better cooling effect (55% improvement over the commercial cotton fiber) can be realized in the a-BN/PVA textile. The wearable a-BN/PVA textiles containing the 3D-printed a-BN/PVA fibers offer a promising selection for meeting the personal cooling requirement, which can significantly reduce the energy consumption and cost for cooling the whole building.
ABSTRACT
Lithium metal anode with the highest capacity and lowest anode potential is extremely attractive to battery technologies, but infinite volume change during the Li stripping/plating process results in cracks and fractures of the solid electrolyte interphase, low Coulombic efficiency, and dendritic growth of Li. Here, we use a carbonized wood (C-wood) as a 3D, highly porous (73% porosity) conductive framework with well-aligned channels as Li host material. We discovered that molten Li metal can infuse into the straight channels of C-wood to form a Li/C-wood electrode after surface treatment. The C-wood channels function as excellent guides in which the Li stripping/plating process can take place and effectively confine the volume change that occurs. Moreover, the local current density can be minimized due to the 3D C-wood framework. Therefore, in symmetric cells, the as-prepared Li/C-wood electrode presents a lower overpotential (90 mV at 3 mAâ cm-2), more-stable stripping/plating profiles, and better cycling performance (â¼150 h at 3 mAâ cm-2) compared with bare Li metal electrode. Our findings may open up a solution for fabricating stable Li metal anode, which further facilitates future application of high-energy-density Li metal batteries.
