Urchin-like Amorphous Nitrogen-Doped Carbon Nanotubes Encapsulated with Transition-Metal-Alloy@Graphene Core@Shell Nanoparticles for Microwave Energy Attenuation

Herein, we report three-dimensional (3D) urchin-like amorphous nitrogen-doped CNT (NCNT) arrays with embedded cobalt-nickel@graphene core@shell nanoparticles (NPs) in the inner parts of NCNTs (CoNi@G@NCNTs) for highly efficient absorption toward microwave (MW). The CoNi NPs are covered with about seven layers of graphene shell, resulting in the formation of CoNi@G core–shell structures. In the meanwhile, the CoNi@G core–shell NPs are further encapsulated within NCNTs. Benefitting from the multiple scattering of the unique 3D structure toward MW, cooperative effect between magnetic loss and dielectric loss, and additional interfacial polarizations, the 3D urchin-like CoNi@G@NCNTs exhibit excellent MW energy attenuation ability with a broad absorption bandwidth of 5.2 GHz with a matching thickness of merely 1.7 mm, outperforming most reported absorbers. Furthermore, the chemical stability of the 3D urchin-like CoNi@G@NCNTs is improved greatly due to the presence of the graphene coating layers and outmost NCNTs, facilitating their practical applications. Our results highlight a novel strategy for fabrication of 3D nanostructures as high-performance MW-absorbing materials

Coupling Hollow Fe₃O₄–Fe Nanoparticles with Graphene Sheets for High-Performance Electromagnetic Wave Absorbing Material

We developed a strategy for coupling hollow Fe₃O₄–Fe nanoparticles with graphene sheets for high-performance electromagnetic wave absorbing material. The hollow Fe₃O₄–Fe nanoparticles with average diameter and shell thickness of 20 and 8 nm, respectively, were uniformly anchored on the graphene sheets without obvious aggregation. The minimal reflection loss <i>R</i>_L values of the composite could reach −30 dB at the absorber thickness ranging from 2.0 to 5.0 mm, greatly superior to the solid Fe₃O₄–Fe/G composite and most magnetic EM wave absorbing materials recently reported. Moreover, the addition amount of the composite into paraffin matrix was only 18 wt %

Hierarchical Cobalt-Doped Molybdenum–Nickel Nitride Nanowires as Multifunctional Electrocatalysts

Herein, we demonstrate hierarchically porous Co-doped MoNi nitride nanowires for multifunctional electrocatalysts. After the Co incorporation for water electrolysis and zinc–air systems, the active surface area is enhanced, whereas the charge-transfer and mass-transfer resistances are reduced significantly. Due to the dual modulation in the electric conductivity and active surface area induced by the Co-doping, the hierarchically porous trimetal nitrides show high activity and good stability for the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction. The two-electrode electrolyzer assembled by the bifunctional electrocatalysts can deliver 10 mA cm–2 at a voltage of merely 1.57 V, compared to the best reported electrocatalysts. Meanwhile, two all-solid-state zinc–air batteries in series can power more than 50 red light-emitting diodes and the two-electrode electrolyzer catalyzed by the multifunctional electrocatalysts with excellent operation stability

Tailoring electronic properties and polarization relaxation behavior of MoS2 monolayers for electromagnetic energy dissipation and wireless pressure micro-sensor

Electromagnetic radiation has become a severe problem due to the widespread utilization of wireless communications and smart electronic devices. Hence, the development of high-performance electromagnetic wave absorbers to overcome the electromagnetic pollution is of utmost significance. Herein, density functional theory (DFT) calculations are adopted to guide the design of high-performance electromagnetic wave absorbers based on layered MoS2. The results indicate that the electronic properties, the dipole moment and the electric polarization of vertically-aligned MoS2 monolayers on N-doped graphene are significantly tuned compared to horizontally-aligned MoS2 monolayers on N-doped graphene and MoS2 nanosheets, favoring the absorption of electromagnetic waves. Based on theoretical predictions, we have combined vertically-aligned MoS2 monolayers and N-doped graphene nanomesh by the spatial confinement effect of the nanomeshs. The experimental results demonstrate that the MoS2 monolayers on N-doped graphene exhibit excellent electromagnetic wave absorption performance with a minimal reflection loss of –72.83 dB and an effective absorption bandwidth of 4.81 GHz even at a matching thickness below 2.0 mm, remarkably outperforming MoS2 nanosheets. The excellent consistency between theoretical and experimental results highlights that the DFT calculations can be employed as a design tool for high-performance electromagnetic wave absorber. Based on the excellent electromagnetic absorption performance of the MoS2 monolayers, a highly sensitive wireless pressure micro-sensor is designed, which has potential apllication in internet of things

Rationally Designed Nanostructure Features on Superhydrophobic Surfaces for Enhancing Self-Propelling Dynamics of Condensed Droplets

The self-propelling ability toward achieving more efficient dropwise condensation intensively appeals to researchers due to its academic significance to explain some basic wetting phenomena. Herein we designed and fabricated the two types of microstructure superhydrophobic surfaces, i.e., sealed layered nanoporous structures (SLP-surface) and open nanocone structures (OC-surface). As a consequence, the resultant surfaces exhibit the robust water repellency, and the water droplet nearly suspends on the superhydrophobic surfaces (CA = 158.8° ± 0.5°, SA = 4° ± 0.5° for the SLP-surface and CA = 160.2° ± 0.4°, SA = 1° ± 0.5° for the OC-surface, respectively). Meanwhile, the impacting droplets can be rapidly rebounded off with a shorter contact time of 11.2 and 10.4 ms (impact velocity V0 = 1 m/s). The excellent static-dynamic superhydrophobicity is mainly attributed to the air pockets captured by both microscopic rough structures. Regarding the self-propelling ability of condensed droplets, it is found that the droplet microscopic pinning effect of the SLP-surface severely weakens the dynamic self-propelling ability of condensed droplets. The capillary adhesive force induced by the sealed layered nanoporous structures is up to 16.0 μN. However, the open nanocone structures cause lower water adhesive force (∼4.1 μN) under the action of flowing air pockets, producing a higher dynamic self-propelling ability of condensed droplets. As a consequence, the open nanocone structure superhydrophobic surface displays a huge potential of inhibiting attachment of condensed droplets

Hollow N‑Doped Carbon Polyhedron Containing CoNi Alloy Nanoparticles Embedded within Few-Layer N‑Doped Graphene as High-Performance Electromagnetic Wave Absorbing Material

Magnetic metal nanostructures have exhibited good electromagnetic wave (EMW) absorption properties. However, the surface of the nanostructures is easily oxidized upon exposure to air, leading to the bad stability of the EMW absorption properties. We use metal–organic framework structure as a template to fabricate hollow N-doped carbon polyhedron containing CoNi alloy nanoparticles embedded within N-doped graphene (CoNi@NG-NCPs). The atomic ratio of Co/Ni can be tuned from 1:0.54 to 1:0.91 in the hollow CoNi@NG-NCPs. Experimental results demonstrate that the EMW absorption properties of the CoNi@NG-NCPs can be improved through the Ni introduction and increased with an increase of the Ni content. Typically, the minimal reflection loss of the optimal CoNi@NG-NCP can reach −24.03 dB and the effective absorption bandwidth (reflection loss below −10 dB) is as large as 4.32 GHz at the thickness of 2.5 mm. Furthermore, our CoNi@NG-NCPs exhibit favorably comparable or superior EMW absorption properties to other magnetic absorbers. In addition, because the CoNi alloy nanoparticles are coated with N-doped graphene layers, their surface oxidation behavior can be efficiently limited. The mechanism of the enhanced EMW absorption property is relevant to the enhanced dielectric loss and better impedance matching characteristic caused by the Ni incorporation

Growth of Ultrathin MoS₂ Nanosheets with Expanded Spacing of (002) Plane on Carbon Nanotubes for High-Performance Sodium-Ion Battery Anodes

A hydrothermal method was developed to grow ultrathin MoS2 nanosheets, with an expanded spacing of the (002) planes, on carbon nanotubes. When used as a sodium-ion battery anode, the composite exhibited a specific capacity of 495.9 mAh g–1, and 84.8% of the initial capacity was retained after 80 cycles, even at a current density of 200 mA g–1. X-ray diffraction analyses show that the sodiation/desodiation mechanismis based on a conversion reaction. The high capacity and long-term stability at a high current ate demonstrate that the composite is a very promising candidate for use as an anode material in sodium-ion batteries

Spraying Fabrication of Durable and Transparent Coatings for Anti-Icing Application: Dynamic Water Repellency, Icing Delay, and Ice Adhesion

Anti-icing/icephobic coatings, typically applied in the form of surface functional materials, are considered to be an ideal selection to solve the icing issues faced by daily life and industrial production. However, the applications of anti-icing coatings are greatly limited by the two main challenges: bonding strength with substrates and stability of the high anti-icing performance. Here, we designed and fabricated a kind of high-performance superhydrophobic fluorinated silica (F-SiO2)@polydimethylsiloxane coatings and further emphasized the improvement of the bonding strength with substrates and the maintenance of high anti-icing performance. The resultant coatings exhibited excellent water repellency with a contact angle up to 155.3° and a very short contact time (∼10.2 ms) of impact droplets. At low temperatures, the coming droplets still rapidly rebounded off the coating surface, and the superhydrophobic coatings displayed a more than 50-fold increase of freezing time comparing with bare aluminum. The ice adhesion strength on the coatings was only 26.3 kPa, which was far less than that (821.9 kPa) of bare aluminum. Furthermore, the nanoporous structures constructed by anodic oxidation could tremendously enhance the bonding strength of the coatings with the substrate, which was evaluated through a standard method (ASTM D3359). The anti-icing properties still retained high stability under the conditions of 30 icing/deicing cycles, soaking, and scouring of acid solution (pH = 5.6). This work can effectively push the anti-icing coatings toward a real-world application

Rationally Designed Nanostructure Features on Superhydrophobic Surfaces for Enhancing Self-Propelling Dynamics of Condensed Droplets

The self-propelling ability toward achieving more efficient dropwise condensation intensively appeals to researchers due to its academic significance to explain some basic wetting phenomena. Herein we designed and fabricated the two types of microstructure superhydrophobic surfaces, i.e., sealed layered nanoporous structures (SLP-surface) and open nanocone structures (OC-surface). As a consequence, the resultant surfaces exhibit the robust water repellency, and the water droplet nearly suspends on the superhydrophobic surfaces (CA = 158.8° ± 0.5°, SA = 4° ± 0.5° for the SLP-surface and CA = 160.2° ± 0.4°, SA = 1° ± 0.5° for the OC-surface, respectively). Meanwhile, the impacting droplets can be rapidly rebounded off with a shorter contact time of 11.2 and 10.4 ms (impact velocity V0 = 1 m/s). The excellent static-dynamic superhydrophobicity is mainly attributed to the air pockets captured by both microscopic rough structures. Regarding the self-propelling ability of condensed droplets, it is found that the droplet microscopic pinning effect of the SLP-surface severely weakens the dynamic self-propelling ability of condensed droplets. The capillary adhesive force induced by the sealed layered nanoporous structures is up to 16.0 μN. However, the open nanocone structures cause lower water adhesive force (∼4.1 μN) under the action of flowing air pockets, producing a higher dynamic self-propelling ability of condensed droplets. As a consequence, the open nanocone structure superhydrophobic surface displays a huge potential of inhibiting attachment of condensed droplets