High-quality ultrathin two-dimensional nanosheets of α-Ni(OH)2 are synthesized at large scale via microwave-assisted liquid-phase growth under low-temperature atmospheric conditions. After heat treatment, non-layered NiO nanosheets are obtained while maintaining their original frame structure. The well-defined and freestanding nanosheets exhibit a micron-sized planar area and ultrathin thickness (<2 nm), suggesting an ultrahigh surface atom ratio with unique surface and electronic structure. The ultrathin 2D nanostructure can make most atoms exposed outside with high activity thus facilitate the surface-dependent electrochemical reaction processes. The ultrathin α-Ni(OH)2 and NiO nanosheets exhibit enhanced supercapacitor performances. Particularly, the α-Ni(OH)2 nanosheets exhibit a maximum specific capacitance of 4172.5 F g−1 at a current density of 1 A g−1. Even at higher rate of 16 A g−1, the specific capacitance is still maintained at 2680 F g−1 with 98.5% retention after 2000 cycles. Even more important, we develop a facile and scalable method to produce high-quality ultrathin transition metal hydroxide and oxide nanosheets and make a possibility in commercial applications.
Ag-doped porous SnO 2 nanopowders were synthesized via a facile glucan-assisted template method combined with subsequent calcinations. Morphology, crystal structure, and H 2 S gas sensing properties of pure and Ag-doped porous SnO 2 nanopowders were investigated. In comparison with undoped SnO 2 nanopowders, the Ag-doped porous SnO 2 nanopowders demonstrated enhanced H 2 S sensing behavior with high sensitivity, short response and recovery time, relatively low response concentration of 50 ppm, and good selectivity. The dramatic improvement in H 2 S gas sensing characteristics was explained in terms of rapid gas diffusion onto the entire sensing surface due to the less-agglomerated and porous structure of SnO 2 nanopowders and the catalytic effect of doped-Ag element. The main objective of this research is to develop a new method to introduce catalysts on gas-sensing materials with less-agglomerated and porous structure.
Multifunctional applications including efficient microwave absorption and electromagnetic interference (EMI) shielding as well as excellent Li-ion storage are rarely achieved in a single material. Herein, a multifunctional nanocrystalline-assembled porous hierarchical NiO@NiFe2 O4 /reduced graphene oxide (rGO) heterostructure integrating microwave absorption, EMI shielding, and Li-ion storage functions is fabricated and tailored to develop high-performance energy conversion and storage devices. Owing to its structural and compositional advantages, the optimized NiO@NiFe2 O4 /15rGO achieves a minimum reflection loss of -55 dB with a matching thickness of 2.3 mm, and the effective absorption bandwidth is up to 6.4 GHz. The EMI shielding effectiveness reaches 8.69 dB. NiO@NiFe2 O4 /15rGO exhibits a high initial discharge specific capacity of 1813.92 mAh g-1 , which reaches 1218.6 mAh g-1 after 289 cycles and remains at 784.32 mAh g-1 after 500 cycles at 0.1 A g-1 . In addition, NiO@NiFe2 O4 /15rGO demonstrates a long cycling stability at high current densities. This study provides an insight into the design of advanced multifunctional materials and devices and provides an innovative method of solving current environmental and energy problems.
Exploring high-performance cathode materials is of great significance for development of rechargeable magnesium batteries. Herein, two-dimensional ultrathin spinel CuCo2S4 nanosheets synthesized via microwave-assisted liquid-phase growth and anion-exchange post-sulfuration method. As a magnesium storage material, the electrochemical behavior of the CuCo2S4 nanosheets is investigated in different voltage ranges. After activated for several cycles in 0.1–2.1 V, the CuCo2S4 nanosheet material can show good electrochemical reversibility between 0.1 and 2.0 V with capacity of 191.4 mAh g−1 (50 mA g−1) and 114.5 mAh g−1 (500 mA g−1). The excellent Mg-storage properties are attributed to the fast kinetics of Mg2+ by the 2D morphology and ternary structure. A conversion reaction of the magnesium ion storage mechanism is confirmed by ex situ X-ray diffraction characterization. The excellent performance of spinel CuCo2S4 nanosheets validates the viability of the multinary strategy and sheds light on the application of 2D material design for cathode research.
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