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Binary transition metal phosphides hold immense potential as innovative electrode materials for constructing high-performance energy storage devices. Herein, porous binary nickel-cobalt phosphide (NiCoP) nanosheet arrays anchored on nickel foam (NF) were rationally designed as self-supported binder-free electrodes with high supercapacitance performance. Taking the combined advantages of compositional features and array architectures, the nickel foam supported NiCoP nanosheet array (NiCoP@NF) electrode possesses superior electrochemical performance in comparison with Ni-Co LDH@NF and NiCoO2@NF electrodes. The NiCoP@NF electrode shows an ultrahigh specific capacitance of 2143 F g-1 at 1 A g-1 and retained 1615 F g-1 even at 20 A g-1, showing excellent rate performance. Furthermore, a binder-free all-solid-state asymmetric supercapacitor device is designed, which exhibits a high energy density of 27 W h kg-1 at a power density of 647 W kg-1. The hierarchical binary nickel-cobalt phosphide nanosheet arrays hold great promise as advanced electrode materials for supercapacitors with high electrochemical performance.

The comprehension of the interactions between the building blocks in hybrids can give us an insight into the design and application of highly efficient electromagnetic wave absorption materials. Herein, we report a facile in situ thermal decomposition route for the fabrication of superparamagnetic Fe 3 O 4 nanocrystals anchored on hydrophobic graphene nanosheets as synergistic electromagnetic wave absorbers. The microstructures and interactions of the Fe 3 O 4 -graphene hybrids are systematically investigated, and the results suggest that the Fe 3 O 4 nanocrystals are uniformly decorated and chemically bonded on the surface of graphene nanosheets without obvious conglomeration or large vacancies. The Fe 3 O 4 -graphene hybrids show hydrophobic and superparamagnetic characteristics. Combing the benefits of superparamagnetic Fe 3 O 4 nanocrystals and electrically conducting graphene, the Fe 3 O 4 -graphene hybrids show a maximum reflection loss (RL) of À40 dB at 6.8 GHz with a matching thickness of 4.5 mm, and the effective absorption bandwidth (RL o À10 dB) is 4.6-18 GHz with an absorber thickness of only 2-5 mm. However, due to the lack of dielectric loss, only a weak RL of À5 dB is obtained in bare Fe 3 O 4 nanocrystals. The remarkably enhanced electromagnetic wave absorption properties of the Fe 3 O 4 -graphene hybrids are owing to effective impedance matching and synergistic interaction. Moreover, compared with other reported graphene-based electromagnetic wave absorption materials, the hydrophobic Fe 3 O 4 -graphene hybridsprepared in this work are considered to be more stable and suitable to be applied in some particular environmental conditions, such as rain.

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