RESUMEN
The composition-tuned, structure-modified, and morphology-controlled nanoscale metal-organic frameworks (MOFs) are quite important to improve the electrochemical performances for supercapacitors. In this work, a solvent-controlled method to prepare amino-functionalized bimetal MOFs with various morphologies is proposed. Three different morphologies of NiCo-MOFs, such as nanospheres, nanosheet-assembled hollow spheres (NSHSs), and rhombus sheets, have been successfully synthesized by using different solvents. The as-prepared three nanoscale NiCo-MOFs are comparatively characterized and are endowed a possible mechanism on nucleation and crystal growth controlling morphology. When used as electrode materials for supercapacitors, all NiCo-MOFs have excellent electrochemical properties. Specifically, the NiCo-MOF NSHS owns the best specific capacitance, which can achieve 1126.7 F g-1 at the current density of 0.5 A g-1 and maintain 93% of its original capacitance at the current density of 10 A g-1 after 3000 charge-discharge cycles. Moreover, an asymmetric supercapacitor device (NiCo-MOF NSHS//AC) assembled with NiCo-MOF NSHS as the positive electrode and activated carbon (AC) as the negative electrode achieves an energy density of 20.94 Wh kg-1 at a power density of 750.84 W kg-1. This work is facile and highly reproducible and can be extended to prepare other nano-MOFs in energy storage and conversion fields. In addition, it opens up an effective approach to synthesizing amino-functionalized MOFs by a solvent-controlled method without any other changes in the experimental conditions.
RESUMEN
Transition metal sulfides are important candidates of battery-type electrode materials for advanced supercapatteries due to their high electric conductivity and electrochemical activity. The Co9S8@Ni3S2/ZnS composite microplate array was prepared by a metal-organic framework-assisted strategy because the electrochemical properties of composite arrays are governed by the synergistic effects of their diverse structures and compositions. As a battery-type material, the Co9S8@Ni3S2/ZnS electrode expressed an ultrahigh areal specific capacity of 8192 C cm-2 at the current density of 2 mA cm-2, and excellent cycling stability of 79.7% capacitance retention after 4000 cycles. An assembled supercapattery device using the Co9S8@Ni3S2/ZnS microplate array as a positive electrode and active carbon as the negative electrode delivered a high energy density of 0.377 mW h cm-2 at a high power density of 1.517 mW cm-2, and outstanding retention of 95.2% after 5000 cycles. As a result, the obtained Co9S8@Ni3S2/ZnS shows potential for applications in high-performance supercapattery.
RESUMEN
Metal-organosulfide coordination polymers (MOSCPs) are important functional materials with attractive application prospects. Herein a two-dimensional structural MOSCP was fabricated on nickel foam with nanosheet array morphology. When as the binder-free battery-type electrode for a supercapacitor, the as-prepared Co-based MOSCP showed high specific capacitance (759 F g-1/379.5 C g-1/105.4 mAh g-1 at 0.5 A g-1), excellent rate performance (58.8% after the current density increased 20 times), and good cycle stability (73.4% after 5000 cycles). In addition, a maximum energy density of 31.97 Wh kg-1 was obtained at a power density of 375.01 W kg-1 in the assembled asymmetric supercapacitor device. These results indicated that this work would open up a new path to design and prepare the battery-type electrode for a supercapacitor by exploring nanoscale MOSCP materials.
RESUMEN
Uniform one-dimensional metal oxide hollow tubular nanofibers (HTNs) have been controllably prepared using a calcination strategy using electrospun polymer nanofibers as soft templates and zeolitic imidazolate framework nanoparticles as precursors. Utilizing the general synthesis method, the ZnO HTNs, Co3O4 HTNs and ZnCo2O4 HTNs have been successfully prepared. The optimal ZnCo2O4 HTNs, as a representative substance applied in supercapacitors as the positive electrode, delivers a high specific capacity of 181 C g-1 at a current density of 0.5 A g-1, an excellent rate performance of 75.14% and a superior capacity retention of 97.42% after 10 000 cycles. Furthermore, an asymmetric supercapacitor assembled from ZnCo2O4 HTNs and active carbon also shows a stable and ultrahigh cycling stability with 95.38% of its original capacity after 20 000 cycle tests.
RESUMEN
Bismuth oxide (Bi2O3) with high specific capacity has emerged as a promising negative electrode material for supercapacitors (SCs). Herein, we propose a facile metal-organic framework (MOF) derived strategy to prepare Bi2O3 microrods with a carbon coat (Bi2O3@C). They exhibit ultrahigh specific capacity (1378 C g-1 at 0.5 A g-1) and excellent cycling stability (93% retention at 4000 cycles) when acting as negative electrode material for advanced asymmetric SCs. The assembled Bi2O3@C//CoNi-LDH asymmetric supercapacitor device exhibits a high energy density of 49 W h kg-1 at a power density of 807 W kg-1. The current Bi-MOF-derived strategy would provide valuable insights to prepare Bi-based inorganic nanomaterials for high-performance energy storage technologies and beyond.
RESUMEN
Bismuth sulfide (Bi2S3) with a lamellar structure has emerged as a promising negative electrode material for supercapacitors (SCs) due to its high theoretical specific capacity. Meanwhile, the improvement of electrochemical properties strongly depends on the size, shape and morphologies of Bi2S3 nanomaterials. Herein, the hierarchical Bi2S3 nanorod-stacked hollow microtubes are self-assembled through a facile self-sacrificing template strategy from bismuth-based metal-organic framework microprisms. Benefiting from the unique structures with a large specific surface area (54.3 m2 g-1), the as-prepared Bi2S3 exhibits an ultrahigh specific capacity (532 C g-1 at 1 A g-1) as a negative electrode for SCs, outperforming other reported Bi2S3 materials.
RESUMEN
To explore the mechanism of cellulose acetate (CA)/thermoplastic polyurethane (TPU) on the fabrication of helical nanofibers, a series of experiments were conducted to find the optimum spinning conditions. The experimental results show that the CA (14 wt%, DMAc/acetone, 1/2 volume ratio)/TPU2 (18 wt%, DMAc/acetone, 3/1 volume ratio) system can fabricate helical nanofibers effectively via co-electrospinning. We focus on the interfacial interaction between the polymer components induced by the polymer structure and intrinsic properties, including solution properties, hydrogen bonding, and miscibility behavior of the two solutions. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) are employed to investigate the interfacial interaction between the two phases of the polymer system. The analysis results provide the explanation of the experimental results that the CA/TPU system has the potential for producing helical nanofibers effectively. This study based on the interfacial interaction between polymer components provides an insight into the mechanism of CA/TPU helical fiber formation and introduces a richer choice of materials for the application of helical fibers.
RESUMEN
Helical fibers in nanoscale have been of increasing interest due to their unique characteristics. To explore the effect of polymer type on helical fiber formation, three polymer systems, Poly(m-phenylene isophthalamide) (Nomex)/polyurethane (TPU), polystyrene (PS)/TPU and polyacrylonitril (PAN)/TPU are used to fabricate helical nanofibers via co-electrospinning. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and Zeta potential were employed to investigate the interfacial interaction between the two phases of the polymer system. The larger rigidity differential of Nomex and TPU leads to a larger interfacial interaction. The hydrogen bonds help to increase the interfacial interaction between Nomex and TPU components. The attractive force between the chloride-ions contained in Nomex molecules and the free charges on the solution surface lead to a longitudinal interfacial interaction in the Nomex/TPU system. The analysis results provide the explanation of the experimental results that the Nomex/TPU system has the greatest potential for producing helical nanofibers, while the PS/TPU and PAN/TPU systems cannot fabricate helical fibers effectively. This study based on the interfacial interaction between polymer components provides an insight into the mechanism of helical fiber formation.
