The
hybrid approach offers opportunities to simultaneously exploit
the features of capacitive (especially carbon) and faradaic (redox
electroactive) materials to increase energy density and power density
of supercapacitors. To achieve an optimized overall electrochemical
performance, we have synthesized a hybrid supercapacitor electrode
consisting of vertically aligned Ni3S2 mesoporous
nanosheets on three-dimensional reduced graphene oxide (Ni3S2/3DrGO) supported by Ni foam with a controllable composition
and morphological structure, which thus improve the electrical conductivity
as well as provide more chemical reaction sites and shorten the migration
path for electrons and ions. By taking advantage of the rational structural
features and excellent electrical conductance ability, the Ni3S2/3DrGO hybrid nanostructure shows greatly improved
electrochemical capacitive performance, including high specific capacitance
of 1886 F g–1 (1621 F g–1) at current density of 1.0 A g–1 (20.0
A g–1) and excellent rate capability and
cycling stability. Remarkably, an all-solid-state symmetric supercapacitor
fabricated by using our pseudocapacitive hybrid nanostructures delivers
a high energy density (58.9 Wh kg–1), high
power density (3.7 kW kg–1 at 45.8 Wh kg–1), and excellent cycling stability (92% capacitance
retention after 30 000 charge–discharge cycles at a
constant current density of 10 A g–1). These
electrochemical performances are superior to those of the previously
reported symmetric supercapacitors, suggesting that these hybrid nanostructures
have a huge potential for high-performance energy conversion and storage
devices.
Polycrystalline TbxNd1−xFe1.9 (0⩽x⩽0.8) cubic Laves phase alloys with MgCu2-type structure were prepared by high-pressure synthesis and subsequent low-temperature annealing. The crystal structure, magnetic properties, and magnetostriction have been investigated. The change of easy magnetic direction from ⟨100⟩ to ⟨111⟩ with increasing x up to 0.1 is detected by Mössbauer spectra. In accordance with Mössbauer effect study, both magnetization and magnetostriction analyses show that TbxNd1−xFe1.9 is an anisotropy compensation system and the compensation point is close to x=0.1. The present work may open an avenue in searching magnetostrictive materials with inexpensive Nd.
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