Zhi Zhang,Qi Lv,Yiwang Chen,Haitao Yu,Hui Liu,Guangzhen Cui,Xiaodong Sun,Ling Li
To reduce electromagnetic pollution as well as increase the accuracy of high-precision electronic equipment, more attention has been paid to new electromagnetic wave (EMW) absorbing materials, which have the advantages of strong absorption, wide absorption bands, and a narrow thickness. In this study, a novel ternary type of the NiS2@rGO/polypyrrole (PPy) sandwich-like structured composites was synthesized via a facile two-step method, in which the hydrothermal method was used to prepare NiS2@rGO binary composites and then the in situ polymerization method was used to synthesize the PPy, which acted as the outer layer of the sandwich-like structure. The morphologies and electromagnetic absorption performance of the NiS2@rGO/PPy were measured and investigated. A sample with 6 wt% NiS2@rGO/PPy loading paraffin-composite obtained an outstanding reflection loss (RL) of −58.7 dB at 16.44 GHz under a thickness of 2.03 mm. Simultaneously, the effective electromagnetic wave absorption bandwidth for RL < −10 dB, which covered 7.04 to 18.00 GHz (10.96 GHz), was achieved by changing the thickness of the absorber from 2.0 to 3.5 mm. The results not only suggest that the NiS2@rGO/PPy composite has excellent performance in the field of EMW absorption but also prove that the novel sandwich-like structure can contribute to appropriate impedance matching through multiple relaxation and interfacial polarization processes.Keywords:graphene;polypyrrole;sandwich-like structure;electromagnetic absorption
To screen out suitable electrode materials and overcome the shortcomings of the existed electrode materials for the application in dye-sensitized solar cells and supercapacitors , NiS 2 /reduced graphene oxide (NiS 2 /rGO) composite material was prepared by a simple one-step hydrothermal method in this paper and applied in the field of both dye-sensitized solar cells and supercapacitors as electrode material. In an electrolyte of 6 M KOH, the NiS 2 /rGO composite material with bilayer capacitance characteristics exhibited a high specific capacitance of 259.20 F g −1 at the current density of 0.6 A g −1 , which was significantly higher than that of rGO (188.94 F g −1 ). Moreover, at a current density of 2 A g −1 , the NiS 2 /rGO composite material had 92.85% capacitance retention after 2000 cycles. When applied as counter electrode material for the dye-sensitized solar cells, the NiS 2 /rGO composite material counter electrode exhibited a satisfactory photoelectric conversion efficiency ( η ) of 3.16% under standard simulated sunlight (AM 1.5 G), which was significantly higher than that of single rGO counter electrode (improved by 90.40%). The NiS 2 /rGO composite electrode material prepared by a simple one-step hydrothermal method is a potential bi-functional composite electrode materials for both dye-sensitized solar cells and supercapacitors.
Herein, molybdenum trisulfide/nickel disulfide-reduced graphene oxide (Mo 2 S 3 /NiS 2 -RGO) composites as anode material for sodium-ion batteries (SIBs) and sodium-ion capacitors (SICs) were synthesized by one-step facile hydrothermal method. Through electron microscopy analysis, it could be observed that the Mo 2 S 3 /NiS 2 nano-rods and nano-balls were dispersed uniformly over the two-dimensional RGO sheets. When tested as an anode material, Mo 2 S 3 /NiS 2 -RGO showed a considerable reversible capacity of 653.1 mA h g −1 at 100 mA g −1 after 50 cycles and capacity retention of 197.5 mA h g −1 at 5000 mA g −1 after 226 cycles. The sodium storage mechanism of Mo 2 S 3 /NiS 2 -RGO was explained by ex situ XPS. Furthermore, as-fabricated SICs delivered an excellent specific energy of 182.7 W h kg −1 (at 1120 W kg −1 ), and SIBs exhibited the discharge capacities of 85 mA h g −1 at 2 C. Overall, the superior electrochemical performances of Mo 2 S 3 /NiS 2 -RGO demonstrated that it was a promising anode materials to construct high-performance full cell.
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