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The microenvironments of metal single‐atoms (SAs) have important effects on their physicochemical properties. However, the understanding of the relationship between the coordination configuration of SAs and their properties is insufficient. Here, a sacrificing template strategy is developed to anchor La‐SAs on interconnected graphene nanocages (La‐N‐Cl/GNC), where La‐SAs are located above the graphene plane and one La atom coordinated with four N atoms in the graphene plane and with one Cl atom along the axial direction. Theoretical calculations demonstrated that asymmetrically La‐SAs are more conducive to breaking local charge symmetry. Consequently, additional electrical dipoles along the axial direction are generated, leading to unprecedented dipolar polarization loss and strong electromagnetic wave absorption properties. Moreover, the film constructed by asymmetrically‐coordinated La‐N‐Cl/GNC with a mass density of 0.084 g cm−3 exhibits superior flexibility, excellent mechanical strength, and moderate thermal insulation properties, guaranteeing its practical applications in harsh environments. These findings not only shed light on the relationships between asymmetrically coordinated SAs and their dielectric properties at the atomic level but also provide an efficient method for preparing multifunctional films. [ABSTRACT FROM AUTHOR]

The understanding of the relationships between the coordination configuration of single-atoms (SAs) and their properties remains a great challenge. In this manuscript, a facile method is developed to construct Fe-SAs on onion-like nitrogen-doped nanocarbons supported by graphene (ONCG). In contrast to the symmetrical planar Fe–N4 moieties, the Fe-SAs coordinated with N atoms are located above the plane of the curved graphene and exhibited antenna-like structures. The ONCG with non-planar Fe–N4 moieties possesses greatly increased dielectric loss property compared to their counterparts with symmetrical planar Fe-SAs. In-depth theoretical calculations reveal that the unique geometric structure of the non-planar Fe-SAs improves both conduction and polarization losses significantly, which is attributed to the increased dielectric property. The increased dielectric property endows Fe-SAs@ONCG with an excellent electromagnetic wave absorption at a low filler ratio of 10 wt. %. Our results describe an efficient way for the development of non-planar SAs for dielectric applications. [ABSTRACT FROM AUTHOR]

The widespread application of high-frequency electronic and communication devices has caused increasingly severe electromagnetic pollution. It is highly desirable but challenging to develop ultralight electromagnetic wave (EMW) absorbers with strong absorption performance to eliminate the negative effects of electromagnetic pollution. Herein, a secondary ion adsorption and defect-anchoring strategy was proposed to construct ultralight N-doped graphene aerogels containing isolated single cobalt atoms (Co-SAs/GAs) with a tunable content of Co-SAs from 1.13 to 2.58 wt. %. The optimal Co-SAs/GAs with a matching thickness of 1.5 mm and an ultralow filler ratio of 5 wt. % attenuated about 99.999% electromagnetic energy and exhibited specific EMW absorption performance (SMAP) of 37 220 dB cm2 g−1, which was 15 000 dB cm2 g−1 higher than that of the best reported absorber in literature. Permittivity and electrical conductivity measurements indicated that the introduction of Co-SAs significantly increased the conduction and polarization losses of the GAs, which was confirmed by simulation results based on the Havriliak–Negami equation. Theoretical calculations demonstrated that the Co–N4 moiety exhibited obvious polarization behavior, which could be further tuned by defective sites in its vicinity. This comprehensive investigation of the relationships between single-atom structure and electromagnetic wave absorption property provides an efficient route toward the rational design of ultralight absorbers with metal single-atoms. [ABSTRACT FROM AUTHOR]

A facile and efficient strategy is developed to incorporate yolk-shell CoO@Co nanoparticles (NPs) and ZnO NPs with graphene sheets. The diameter and the space between CoO shell and Co yolk are merely 12.0 nm and 1.0 nm, respectively, while the diameter of ZnO NPs is in the range of 4.0–10.0 nm. Due to the small size of NPs and the special structural feature, the resultant graphene-based composite exhibits excellent electromagnetic wave (EMW) absorption properties. Typically, the minimal reflection loss ( R L ) value reaches to −51.1 dB at 11.3 GHz at the absorber thickness of 2.6 mm, and less than −20 dB at the absorber thickness ranging from 2.0 to 5.0 mm. Moreover, the absorption bandwidths corresponding to the R L values below −10 dB (90% of EMW wave energy consumption) is up to 4.7 GHz (from 9.5 to 14.2 GHz) at a thickness of 2.6 mm. Furthermore, the addition amount of the composite into paraffin matrix is merely 20 wt%, less than that of most EMW absorber reported previously. Therefore, such novel hybrid materials can be used as a kind of candidate for lightweight EMW absorbing material. [ABSTRACT FROM AUTHOR]

A general strategy based on the nanoscale Kirkendall effect has been developed to grow hollow transition metal (Fe, Co or Ni) oxide nanoparticles on graphene sheets. When applied as lithium-ion battery anodes, these hollow transition metal oxide-based composites exhibit excellent electrochemical performance, with high reversible capacities and long-term stabilities at a high current density, superior to most transition metal oxides reported to date. [ABSTRACT FROM AUTHOR]

Charged up: Three‐dimensional architectures constructed from graphene/MoS2 nanoflake arrays have been successfully fabricated by a one‐step hydrothermal method. MoS2 nanoflakes with thicknesses less than 13 nm grow vertically on both sides of graphene sheets (see figure), which allows the architectures to be more stable during charging and discharging. Even at a high current density of 8000 mA g−1, their discharge capacity is still up to 516 mA h g−1. [ABSTRACT FROM AUTHOR]

Graphene (G)-Fe3O4 nanohybrids were fabricated by first depositing β-FeOOH crystals with diameter of 3-5 nm on the surface of the graphene sheets. After annealing under Ar flow, β-FeOOH nanocrystals were reduced to Fe3O4 nanoparticles by the graphene sheets, and thus G-Fe3O4 nanohybrids were obtained. The Fe3O4 nanoparticles with a diameter of about 25 nm were uniformly dispersed over the surface of the graphene sheets. Moreover, compared with other magnetic materials and the graphene, the nanohybrids exhibited significantly increased electromagnetic absorption properties owing to high surface areas, interfacial polarizations, and good separation of magnetic nanoparticles. The maximum reflection loss was up to -40.36 dB for G-Fe3O4 nanohybrids with a thickness of 5.0 mm. The nanohybrids are very promising for lightweight and strong electromagnetic attenuation materials. [ABSTRACT FROM AUTHOR]

A general strategy based on the nanoscale Kirkendall effect is developed to grow hollow transition metal (Fe, Co or Ni) oxide nanoparticles on graphene sheets. When applied as lithium‐ion battery anodes, these hollow transition metal oxide based composites exhibit excellent electrochemical performance with high reversible capacities and long‐term stabilities at a high current density, superior to most transition metal oxides reported to date. More information can be found in the Full Paper by Y. Chen, C. Sun, P. Gao et al. on page 1638 ff. [ABSTRACT FROM AUTHOR]

The increasingly serious electromagnetic radiation urgently call for high performance electromagnetic wave (EMW) absorbers. Hollow carbon nanostructures are promising for lightweight EMW absorbers. However, due to lack of sufficient polarization centers, the EMW absorption property of hollow carbon nanosturctures is still unsatisfactory. Herein, we develop a double-salt template method for fabrication of N, S-codoped graphitic carbon nanoframes (GF) that anchored on the graphene sheets (GS). The GFs in the sample (N, S-GF/GS) have a width of about 51 nm and a wall thickness of only 4.8 nm. Furthermore, the graphene plane in the GF is perpendicular to the graphene plane in the GS, leading to the formation of numerous interfaces between the graphene planes perpendicular to each other. Theoretical calculations indicate that the interfaces can induce the interfacial polarization loss, and the N, S co-doping can cause dipole polarization loss, both of which enhance the EMW absorption performance of the N, S-GF/GS. The minimal reflection loss and efficient absorption width of the N, S-GF/GS at a low filler ratio of 10 wt% are -45.64 dB at the matching thickness of 2.3 mm and 4.35 GHz with the thickness of 1.5 mm, respectively, superior to most of carbon-based absorbers. Our proposed method opens a promising way for high-performance EMW absorbers. [Display omitted] • A double-salt template method was proposed for fabricating N, S-codoped carbon nanoframes (GF) on graphene (GS). • The GFs have a width of about 51 nm and a wall thickness of only 4.8 nm. • The graphene planes in GF and GS are perpendicular to each other, leading to numerous interfaces. • The effective absorption bandwidth of the designed absorbers reached 4.35 GHz. • The mechanism about the synergisty of interface and N, S co-doping was uncovered. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) graphene-based structures have attracted much attention due to their unique physicochemical properties and potential applications in various fields. In this work, we develop a facile strategy for growing Co and Zn-contained nitrogen-doped carbon nanotubes on the graphene sheets for the absorption of electromagnetic wave (EMW). The as-fabricated 3D structures with a larger surface area have high electrical conductivities, abundant defects, numerous interfaces and porous feature, endowing them to excellent EMW absorption performance. The minimal reflection loss and efficient absorption bandwidth of the optimized 3D structure can reach to −47.31 dB and 4.01 GHz at a low thickness of merely 1.5 mm, respectively. Even at the thickness of 1.2–1.5 mm, the minimal reflection losses are less than −10 dB. Furthermore, the filler mass loading of the 3D structures is only 6 wt%, lower than those of most of the reported absorbers. Our results highlight the importance of 3D structures composed of graphene and nitrogen-doped carbon nanotubes to high-efficiency EMW absorption. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Nitrogen-doped carbon sheets containing Fe 3 C nanoparticles encapsulated in nitrogen-doped graphene shells are fabricated through heating the mixture of urea and ferric acetylacetonate and the subsequent treatment in hot acid solution. The nitrogen-doped carbon sheets have a lateral length ranging from hundred nanometers to several micrometers, while the Fe 3 C nanoparticles encapsulated in nitrogen-doped graphene have a diameter of approximately 60 nm. The nitrogen-doped carbon sheets exhibit excellent electromagnetic wave absorption property. Typically, the optimal sample has the effective absorption bandwidth of 6.0 GHz at the absorber thicknesses of only 2.0 mm, favorably comparable to those of the magnetic absorbers reported previously. The excellent electromagnetic wave absorption property of nitrogen-doped carbon sheets containing Fe 3 C nanocapsules encapsulated in the nitrogen-doped graphene shells can be explained by their better impedance matching character and enhanced dielectric loss. Graphical abstract The optimal sample has the effective absorption bandwidth of 6.0 GHz at the absorber thicknesses of only 2.0 mm. Image 1 [ABSTRACT FROM AUTHOR]

Highlights: [•] Graphene/Fe nanocomposites were prepared by a facile and green method. [•] 10nm Fe nanoparticles were uniformly dispersed over the surface of the graphene sheets. [•] The nanocomposites exhibited strong electromagnetic wave absorption properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D hollow FeP nanostructures arrays on the graphene (3D FeP NT/PG) are fabricated. • Adopted electrostatic-repulsion-limited-nucleation strategy and Kirkendall effect. • The FeP NTs are about 100 and 25 nm in length and diameter, respectively. • The 3D FeP NT/PG exhibits superior HER catalytic activity and long-term stability. • The synergistic effect between FeP and G are proved by the DFT calculations. It is highly desirable but still challenging to construct three-dimensional (3D) open porous structure assembled with small-sized and hollow active components for hydrogen evolution reaction (HER). Here, we propose a novel protocol based on electrostatic-repulsion-limited-nucleation strategy and the nanoscale Kirkendall effect to grow FeP nanotube arrays on P-doped graphene. Due to its unique structural features, the resulting electrocatalyst exhibits superior HER activity with an overpotential of 69 mV at the current density of 10 mA cm−2 in 0.5 M H 2 SO 4 , comparable to the benchmark Pt/C catalyst. Furthermore, the 3D porous structure shows robust stability toward HER with a negligible current loss after continuous catalysis over 40 h at 10 mA cm−2. The experimental results and density functional theory calculations indicate that the excellent HER activity of the 3D porous structure originates from its increased active sites, reduced transfer resistance and the ideal hydrogen adsorption energy (Δ G H*), as well as better hydrophily upon integration of FeP nanotubes with P-doped graphene. Our protocol provides a new approach to rationally design and fabricate inexpensive 3D open porous structure with high catalytic activity and robust stability for HER. [ABSTRACT FROM AUTHOR]

In this study, nitrogen (N)-doped graphene-coated FeNi nanoparticles were fabricated onto N-doped carbon (NC) nanosheets (FeNi@NGLs/NC) by a simple method. The simulations based on the Havriliak–Negami (H–N) model show two relaxation peaks resulting from the dipole and interfacial polarizations in the dielectric spectra of FeNi@NGLs/NC, Ni@NGLs/NC, and Fe 3 C/Fe@NGLs/NC. Among these samples, Ni@NGLs/NC exhibits the largest dielectric loss, which is related to its high conduction loss below 8 GHz and relaxation loss over the range 2–18 GHz. Through simulations based on the Gilbert modification of the Landau–Lifshitz equation, different numbers of resonance peaks are derived from the permeability-frequency plots of these samples. Further theoretical calculations indicate that the number and position of these resonance peaks are dependent on the type of metal nanoparticles (NPs) in the samples. Despite having the largest dielectric loss, Ni@NGLs/NC exhibits the worst electromagnetic wave (EMW) absorption properties among the three samples, because of its poor impedance matching characteristics, caused by the skin effect. These results not only uncover the origin of dielectric and magnetic losses in magnetic carbon composites, but also demonstrate the importance of the balance between the loss and impedance matching for an EMW absorber. • N-doped graphene-coated FeNi nanoparticles on N-doped carbon nanosheets (FeNi@NGLs/NC) were obtained using a simple method. • The permittivity and permeability of FeNi@NGLs/NC were discussed based on the H–N model and LLG equation. • FeNi@NGLs/NC exhibited excellent electromagnetic wave (EMW) absorption property. • Our results indicated the importance of the balance between loss and impedance matching characteristics to EMW absorption. [ABSTRACT FROM AUTHOR]