Multispectral camouflage and radiative cooling using dynamically tunable metasurface.

With the increasing demand for privacy, multispectral camouflage devices that utilize metasurface designs in combination with mature detection technologies have become effective. However, these early designs face challenges in realizing multispectral camouflage with a single metasurface and restricted modes. Therefore, this paper proposes a dynamically tunable metasurface. The metasurface consists of gold (Au), antimony selenide (Sb2Se3), and aluminum (Al), which enables radiative cooling, light detection and ranging (LiDAR) and infrared camouflage. In the amorphous phase of Sb2Se3, the thermal radiation reduction rate in the mid wave infrared range (MWIR) is up to 98.2%. The echo signal reduction rate for the 1064 nm LiDAR can reach 96.3%. In the crystalline phase of Sb2Se3, the highest cooling power is 65.5 Wm-2. Hence the metasurface can reduce the surface temperature and achieve efficient infrared camouflage. This metasurface design provides a new strategy for making devices compatible with multispectral camouflage and radiative cooling.

Integrated Design for Discrete Sulfur@Polymer Nanoreactor with Tandem Connection as Lithium-Sulfur Battery Cathodes.

Apart from electrode material modification, architecture design and optimization are important approaches for improving lithium-sulfur battery performance. Herein, an integrated structure with tandem connection is constructed by confining nanosulfur (NS) in conductive poly(3,4-ethylenedioxythiophene) (PEDOT) reaction chambers, forming an interface of discrete independent nanoreactor units bonded onto carbon nanotubes (noted as CNT/NS@PEDOT). The unique spatial confinement and concentration gradients of sulfur@PEDOT nanoreactors (SP-NRs) can promote reaction kinetics while facilitating rapid polysulfide transformation and minimizing dissolution and diffusion losses. Meanwhile, overall ultrahigh energy input and output are achieved through tandem connection with carbon nanotubes, isolation with PEDOT coating, and synergistic multiplicative effects among SP-NRs. As a result, it delivers a high initial discharge capacity of 1246 mAh g-1 at 0.1 C and 918 mAh g-1 at 1 C, the low capacity decay rate per lap of 0.011 % is achieved at a current density of 1 C after 1000 cycles. This research emphasizes the innovative structural design to provide a fresh trajectory for the further advancement of high-performance energy storage devices.

Boosting Fast Sodium Ion Storage by Synergistic Effect of Heterointerface Engineering and Nitrogen Doping Porous Carbon Nanofibers.

Heterointerface engineering with multiple electroactive and inactive supporting components is considered an efficient approach to enhance electrochemical performance for sodium-ion batteries (SIBs). Nevertheless, it is still a challenge to rationally design heterointerface engineering and understand the synergistic effect reaction mechanisms. In this paper, the two-phase heterointerface engineering (Sb2 S3 and FeS2 ) is well designed to incorporate into N-doped porous hollow carbon nanofibers (Sb-Fe-S@CNFs) by proper electrospinning design. The obtained Sb-Fe-S@CNFs are used as anode in SIBs to evaluate the electrochemical performance. It delivers a reversible capacity of 396 mA h g-1 after 2000 cycles at 1 A g-1 and exhibits an ultra-long high rate cycle life for 16 000 cycles at 10 A g-1 . The admirable electrochemical performance is mainly attributed to the following reasons: The porous carbon nanofibers serve as an accelerator of the electrons/ions and a buffer to alleviate volume expansion upon long cyclic performance. The abundant phase boundaries of Sb2 S3 /FeS2 exert low Na+ adsorption energy and greatly promote the charge transfer in the internal electric field calculated by first-principle density functional theory. Therefore, the as-prepared Sb-Fe-S@CNFs represents a promising candidate for an efficient anode electrode material in SIBs.

The effects of vacancy and heteroatoms-doping on the stability, electronic and magnetic properties of blue phosphorene.

In this work, we have systematically studied the stability, electronic structure and magnetic properties of the pristine, four defect states case of blue phosphorene and the six heteroatoms doping in blue phosphorene by first-principles calculations. In our findings, both defects and heteroatoms doping can regulate the band gap of blue phosphorene and the transition from indirect to direct band gap can be dramatically tuned by DV1BP, DV2BP and Al, Si atoms substitutional doping in blue phosphorene. The presence of defects and heteroatoms doping effectively modulates the electronic properties of blue phosphorene, rendering the defect-containing phosphorene semiconducting with a tunable band gap. Spin-orbit coupling can be induced by introducing SV-, DV- defects in blue phosphorene. The results provide theoretical guidance for future bandgap regulation and magnetism, defective and substitutional doping blue phosphorene may have potential electro-optical and electromagnetic applications.

Chip-Inspired Design of High-Performance Lithium-Sulfur Batteries by Integrating Monodisperse Sulfur Nanoreactors on Graphene.

For practical application of lithium-sulfur batteries (LSBs), designing devices with an overall optimal structure instead of modifying electrode materials is significant. Herein, we report a chip-inspired design of a vertically integrated structure as an LSB cathode by implanting Mo2C nanoparticles and nanosulfur into the reduced graphene oxide (rGO) matrix. This configuration enabled the synthesis of isolated sulfur nanoreactors (S-NRs) integrated in a tandem array on the rGO, generating chip-like integrated LSBs. The spatial confinement/protection and concentration gradient of the S-NRs effectively avoided the dissolution, diffusion, and loss of polysulfides, thereby enhancing the sulfur utilization and redox reaction kinetics. Additionally, the adaptive storage energy can be improved by utilizing the tandem, isolation, and synergistic multiplicative effect among the nanoreactor units. As a result, the integrated LSB cathode obtained excellent electrochemical performances with an initial capacity of 1392 mAh g-1 at 0.1C, a low capacity decay rate of 0.017% per cycle during 1500 cycles of operation at 0.5C, and a superior rate performance. This work provides a rational design idea and method of further advancing the precise preparation of high-performance energy storage devices.

Improving the Photocatalytic Activity of Ti3C2 MXene by Surface Modification of N Doped.

Methyl orange dye (MO) is one of the azo dyes, which is not only difficult to degrade but also hazardous to human health, therefore, it is necessary to develop an efficient photocatalyst to degrade MO. In this paper, a facile and low-cost elemental doping method was used for the surface modification of Ti3C2 MXene, i.e., nitrogen-doped titanium carbide was used as the nitrogen source, and the strategy of combining solvent heat treatment with non-in situ nitrogen doping was used to prepare N-Ti3C2 MXene two-dimensional nanomaterials with high catalytic activity. It was found that the catalytic efficiency of N-Ti3C2 MXene materials was enhanced and improved compared to the non-doped Ti3C2 MXene. In particular, N-Ti3C2 1:8 MXene showed the best photo-catalytic ability, as demonstrated by the fact that the N-Ti3C2 1:8 MXene material successfully degraded 98.73% of MO (20 mg/L) under UV lamp irradiation for 20 min, and its catalytic efficiency was about ten times that of Ti3C2 MXene, and the N-Ti3C2 photo-catalyst still showed good stability after four cycles. This work shows a simplified method for solvent heat-treating non-in situ nitrogen-doped Ti3C2 MXene, and also elaborates on the photo-catalytic mechanism of N-Ti3C2 MXene, showing that the high photo-catalytic effect of N-Ti3C2 MXene is due to the synergistic effect of its efficient charge transfer and surface-rich moieties. Therefore, N-Ti3C2 MXene has a good prospect as a photo-catalyst in the photocatalytic degradation of organic pollutants.

Synergistic capture and conversion of polysulfides in cathode composites with multidimensional framework structures.

The application of lithium-sulfur batteries are seriously hindered by their poor cycle stability and low sulfur utilization due to their inevitable polysulfide shuttle effect and slow reaction kinetics. Here, Mo2C nanorods that were surface-decorated with metallic-organic framework-derived nitrogen-doped carbon and ultrasmall cobalt nanoparticles (NC-Co@Mo2C) were used as the materials for lithium-sulfur battery cathodes. The prepared NC-Co@Mo2C@S composites had the specific capacity of 1073 mAh·g-1 (0.2 C) and the retained 806 mAh·g-1 after 200 cycles, thus showing excellent discharge specific capacity and cycling stability. The Mo2C nanorods can adsorb lithium polysulfides (LiPSs) through the formation of MoS bonds. Cobalt nanoparticles electrocatalytically accelerated the redox kinetic conversion of LiPSs. Nitrogen doping can effectively reduce the energy potential barrier. The interconnected multidimensional backbone of NC-Co@Mo2C composites contributed to electrolyte permeation, fast electron/Li+ transport, and sufficient volume change buffering. Therefore, the synergistic effect of the adsorption ability of Mo2C nanorods and the catalytic ability of cobalt nanoparticles can effectively improve the sulfur fixation ability of the composites and greatly suppress the shuttle effect.

Effects of Deposition and Annealing Temperature on the Structure and Optical Band Gap of MoS2 Films.

In this study, molybdenum disulfide (MoS2) film samples were prepared at different temperatures and annealed through magnetron sputtering technology. The surface morphology, crystal structure, bonding structure, and optical properties of the samples were characterized and analyzed. The surface of the MoS2 films prepared by radio frequency magnetron sputtering is tightly coupled and well crystallized, the density of the films decreases, and their voids and grain size increase with the increase in deposition temperature. The higher the deposition temperature is, the more stable the MoS2 films deposited will be, and the 200 °C deposition temperature is an inflection point of the film stability. Annealing temperature affects the structure of the films, which is mainly related to sulfur and the growth mechanism of the films. Further research shows that the optical band gaps of the films deposited at different temperatures range from 0.92 eV to 1.15 eV, showing semiconductor bandgap characteristics. The optical band gap of the films deposited at 200 °C is slightly reduced after annealing in the range of 0.71-0.91 eV. After annealing, the optical band gap of the films decreases because of the two exciton peaks generated by the K point in the Brillouin zone of MoS2. The blue shift of the K point in the Brillouin zone causes a certain change in the optical band gap of the films.

Preparation of Copper Nitride Films with Superior Photocatalytic Activity through Magnetron Sputtering.

TiO2 possesses a wide forbidden band of about 3.2 eV, which severely limits its visible light absorption efficiency. In this work, copper nitride (Cu3N) films were prepared by magnetron sputtering at different gas flow ratios. The structure of the films was tested by scanning electron microscope, X-ray diffractometer, and X-ray photoelectron spectroscope. Optical properties were investigated by UV-vis spectrophotometer and fluorescence spectrometer. Results show that the Cu3N crystal possesses a typical anti-ReO3 crystal structure, and the ratio of nitrogen and Cu atoms of the Cu3N films was adjusted by changing the gas flow ratio. The Cu3N films possess an optical band gap of about 2.0 eV and energy gap of about 2.5 eV and exhibit excellent photocatalytic activity for degrading methyl orange (degradation ratio of 99.5% in 30 min). The photocatalytic activity of Cu3N mainly originates from vacancies in the crystal and Cu self-doping. This work provides a route to broaden the forbidden band width of photocatalytic materials and increase their photoresponse range.

Preparation of Cu3N/MoS2 Heterojunction through Magnetron Sputtering and Investigation of Its Structure and Optical Performance.

Cu3N/MoS2 heterojunction was prepared through magnetron sputtering, and its optical band gap was investigated. Results showed that the prepared Cu3N/MoS2 heterojunction had a clear surface heterojunction structure, uniform surface grains, and no evident cracks. The optical band gap (1.98 eV) of Cu3N/MoS2 heterojunction was obtained by analyzing the ultraviolet-visible transmission spectrum. The valence and conduction band offsets of Cu3N/MoS2 heterojunction were 1.42 and 0.82 eV, respectively. The Cu3N film and multilayer MoS2 formed a type-II heterojunction. After the two materials adhered to form the heterojunction, the interface electrons flowed from MoS2 to Cu3N because the latter had higher Fermi level than the former. This behavior caused the formation of additional electrons in the Cu3N and MoS2 layers and the change in optical band gap, which was conducive to the charge separation of electrons in MoS2 or MoS2 holes. The prepared Cu3N/MoS2 heterojunction has potential application in various high-performance photoelectric devices, such as photocatalysts and photodetectors.

High-Performance Lithium-Sulfur Batteries With an IPA/AC Modified Separator.

To inhibit the polysulfide-diffusion in lithium sulfur (Li-S) batteries and improve the electrochemical properties, the commercial polypropylene (PP) was decorated by an active carbon (AC) coating with lots of electronegative oxygenic functional group of -OH. Owing to the strong adsorption of AC and the electrostatic repulsion between the -OH and negatively charged polysulfide ions, the Li-S batteries demonstrated a high initial discharge capacity of 1,656 mAh g-1 (approximately 99% utilization of sulfur) and the capacity can still remain at 830 mAh g-1 after 100 cycles at 0.2 C. Moreover, when the rate was increased to 1 C, the batteries could also possess a discharge capacity of 1,143 mAh g-1. The encouraging cycling stability make clear that this facile approach can successfully restrain the shuttle effect of polysulfides and make further progress to the practical application of Li-S batteries.

Preparation of ZnFe2O4/α-Fe2O3 Nanocomposites From Sulfuric Acid Leaching Liquor of Jarosite Residue and Their Application in Lithium-Ion Batteries.

Recycling Zn and Fe from jarosite residue to produce high value-added products is of great importance to the healthy and sustainable development of zinc industry. In this work, we reported the preparation of ZnFe2O4/α-Fe2O3 nanocomposites from the leaching liquor of jarosite residue by a facile chemical coprecipitation method followed by heat treatment at 800°C in air. The microstructure of the as-prepared ZnFe2O4/α-Fe2O3 nanocomposites were characterized by X-ray diffraction (XRD), Mössbauer spectroscopy, scanning transmission electron microscope (STEM), and X-ray photoelectron spectrum (XPS). The results demonstrated that the ZnFe2O4/α-Fe2O3 composites are composed of interconnected ZnFe2O4 and α-Fe2O3 nanocrystals with sizes in the range of 20-40 nm. When evaluated as anode material for Li-ion batteries, the ZnFe2O4/α-Fe2O3 nanocomposites exhibits high lithium storage activity, superior cyclic stability, and good high rate capability. Cyclic voltammetry analysis reveals that surface pseudocapacitive lithium storage has a significant contribution to the total stored charge of the ZnFe2O4/α-Fe2O3, which accounts for the enhanced lithium storage performance during cycling. The synthesis of ZnFe2O4/α-Fe2O3 nanocomposites from the leaching liquor of jarosite residue and its successful application in lithium-ion batteries open up new avenues in the fields of healthy and sustainable development of industries.

Plane Double-Layer Structure of AC@S Cathode Improves Electrochemical Performance for Lithium-Sulfur Battery.

Due to the high theoretical specific capacity of lithium-sulfur batteries, it is considered the most promising electrochemical energy storage device for the next generation. However, the development of lithium-sulfur battery has been restricted by its low cycle efficiency and low capacity. We present a Plane double-layer structure of AC@S cathode to improve the electrochemical performance of lithium-sulfur batteries. The battery with this cathode showed good electrochemical performance. The initial discharge capacity of the battery with the structure of AC@S cathode could reach 1,166 mAhg-1 at 0.1 C. After 200 cycles, it still remains a reversible capacity of 793 mAh g-1 with a low fading rate of 0.16% per cycle. Furthermore, the batteries could hold a discharge capacity of 620 mAh g-1 after 200 cycles at a typical 0.5 C rate. The improvement of electrochemical performance is attributed to that the polysulfide produced during charge/discharge can be better concentrated in the cathode by the planar double-layer structure, thus reducing the loss of sulfur.