RESUMEN
As supercapacitor electrode materials, their structures, including specific surface area, instability, and interconnection, determine the electrochemical performances (specific capacitance, cycle stability, and rate performance). In this study, 1T-MoS2 nanosheets were self-assembled into nanoflowers via a one-pot facile hydrothermal reaction. The nanoflowers retain the excellent electrical conductive performance and the feature of inherent high specific surface area of the nanosheets. For the sheets are interconnected to each other in flower structure, the structure is more stable and the charges are more easily transferred. Thus, compared to the nanosheet electrode, the nanoflower electrode shows the remarkable advantage when used as the electrode of the energy-storage device, whether it is 1T phase or 2H phase in KCl or in KOH. When measured at 0.5 A g-1 in KOH electrolyte, the MoS2 nanoflower electrode exhibits a high specific capacitance of 1120 F g-1. At the same time, when cycling 2000 times at a current density of 10 A g-1, the capacitance retention ratio can reach up to 96%.
RESUMEN
It is well-known that in neutral and acidic aqueous electrolytes, MoS2 monolayers can store charges by adsorption of cations on to the electrode-electrolyte interface as its analog of graphene. Restricted by its low conductivity and the charge storage mechanism, the electrochemical performance of MoS2 monolayer supercapacitor electrode is not satisfactory. It is reported here that water bilayers absorbed on MoS2 monolayers can be involved in charge storage. One proton of each absorbed water molecule can intercalate/de-intercalate the water bilayers during charging/discharging in the alkaline aqueous electrolyte. For two water molecules are present for every Mo atom, the water bilayers can endow MoS2 monolayers an ultrahigh specific capacitance. In this paper, 1T phase MoS2 nanosheets with three monolayers were synthesized by hydrothermal reaction. It presents a specific capacitance of 1120 F g-1 at a current density of 0.5 A g-1 in KOH. As it is assembled with active carbon into a hybrid supercapacitor, the device has an energy density of 31.64 Wh kg-1 at a power density of 425 W kg-1, and gets a specific capacitance retention of 95.4% after 10,000 cycles at 2 A g-1.
RESUMEN
Traditional oil-water separation materials have to own ultrahigh or ultralow surface energy. Thus, they can only be wetted by one of the two, oil or water. Our experiment here demonstrates that the wettability in oil-water mixtures can be tuned by oil and water initially. Hierarchical voids are built on commercial copper foams with the help of hydrothermally synthesized titanium dioxide nanorods. The foams can be easily wetted by both oil and water. The water prewetted foams are superhydrophilic and superoleophobic under oil-water mixtures, meanwhile the oil prewetted foams are superoleophilic and superhydrophobic. In this paper, many kinds of water-oil mixtures were separated by two foams, prewetted by corresponding oil or water, respectively, combining a straight tee in a high flux, high efficiency, and continuous mode. This research indicates that oil-water mixtures can be separated more eco-friendly and at lower cost.
RESUMEN
Ultrathin dual phase nanosheets consisting of alternating spinel Li4Ti5O12 (LTO) and rutile TiO2 (RT) lamellas are synthesized through a facile and scalable hydrothermal method, and the formation mechanism is explored. The thickness of constituent lamellas can be controlled exactly by adjusting the mole ratio of Li:Ti in the original reactants. Alternating insertion of the RT lamellas significantly improves the electrochemical performance of LTO nanosheets, especially at high charge/discharge rates. As anodes in lithium-ion batteries (LIBs), the dual phase nanosheet electrode with the optimized phase ratio can deliver stable discharge capacities of 178.5, 154.9, 148.4, 142.3, 138.2, and 131.4 mA h g-1 at current densities of 1, 10, 20, 30, 40, and 50 C, respectively. Meanwhile, they inherit the excellent cyclic stability of pure spinel LTO and exhibit a capacity retention of 93.1% even after 500 cycles at 50 C. Our results indicate that the alternating nanoscaled lamella structure is a good alternative to facilitate the transfer of both the Li ions and electrons into the spinel LTO, giving rise to an excellent cyclability and fast rate performance. Therefore, the newly prepared carbon-free LTO-RT nanosheets with high safety provide a new opportunity to develop high-power anodes for LIBs.
RESUMEN
Practical application of superhydrophobic surfaces is limited by the fragility of nanoscale asperities. Combining chemical etching and anodization, microscale pits and nanoscale pores, instead of the micro and nano protrusions on traditional superhydrophobic surfaces mimicking Lutos leaves, were fabricated on commercially pure aluminum surfaces. After modified by FDTS, the surfaces were superhydrophobic and self-cleaning. The ultrahigh hardness and electrochemical stability of Al2O3 coating endowed the surface excellent mechanical durability and good corrosion resistance. Because the method is scalable, it may find practical application on body panels of automobiles and aircrafts and so on.
RESUMEN
A high-performance anode material for lithium storage was successfully synthesized by glucose as carbon source and cobalt nitrate as Co3O4 precursor with the assistance of sodium chloride surface as a template to reduce the carbon sheet thickness. Ultrafine Co3O4 nanoparticles were homogeneously embedded in ultrathin porous graphitic carbon in this material. The carbon sheets, which have large specific surface area, high electronic conductivity, and outstanding mechanical flexibility, are very effective to keep the stability of Co3O4 nanoparticles which has a large capacity. As a consequence, a very high reversible capacity of up to 1413 mA h g(-1) at a current density of 0.1 A g(-1) after 100 cycles, a high rate capability (845, 560, 461 and 345 mA h g(-1) at 5, 10, 15 and 20 C, respectively, 1 C = 1 A g(-1)), and a superior cycling performance at an ultrahigh rate (760 mA h g(-1) at 5 C after 1000 cycles) are achieved by this lithium-ion-battery anode material.
RESUMEN
Ultrathin mesoporous NiCo2 O4 nanosheets were directly grown on Ni foams to form an efficient and reversible anode for lithium-ion half-cell batteries. Nanosheets with wrinkles, which were monolayers of 10â nm NiCo2 O4 nanoparticles, were interconnected to build up a honeycomb-like architecture that offered a large electrolyte contact area and good structural integrity. The firm attachment of the sheets on the foam endows the anode with good electrical conductivity and excellent mechanical stability. Electrochemical measurements confirm that the electrode has a better performance at reversible Li+ storage (specific capacity of 1170.1â mA h g-1 in the 50th cycle at 0.2â C) than the pasted electrode made of NiCo2 O4 nanosheets powder.