A template-free two-step strategy is successfully developed for the low-cost one pot production of Ni0.33Co0.66(OH)F hollow hexagons woven by multi-walled carbon nanotubes (MWCNTs).
Developing supercapacitors with simultaneous superior power and energy density for energy-storage devices remains a challenge. In this work, single-phase NiS2 microflowers were synthesized through a hydrothermal process coupled with subsequent sulfidation. The obtained NiS2 microflowers perfectly inherited the flowerlike structure of the precursor, which was composed of nanosheets with firmly integrated nanoparticles. With the benefit of the single-phase crystal structure, suppressed surface oxidation, relatively high apparent conductivity, and unique nano/microstructure, the NiS2 microflowers presented outstanding electrochemical performance in the LiOH electrolyte. Specifically, the NiS2 microflowers exhibited high specific capacities of 813 C g–1 at 1 A g–1 and 580 C g–1 at 20 A g–1 and retained 93% of its initial capacity after 10,000-time cycling test. Moreover, an optimized NiS2//activated carbon (AC) hybrid supercapacitor fabricated with NiS2 microflowers as the positive electrode and AC as the negative electrode operated stably at a large voltage window of 1.8 V. It further delivered a considerable energy density of 39.8 W h kg–1 at 900 W kg–1. Impressively, the intriguing nano/microstructure further endowed the almost unabated capacitance after continuous cycling of 10,000 times. This study will definitely promote the design and preparation of high-performance nickel-based sulfides for hybrid supercapacitors.
Ultra-sensitive and highly selective detection of glucose is essential for the clinical diagnosis of diabetes. In this paper, an ultra-sensitive glucose sensor was successfully fabricated based on cobalt oxide (Co3O4) nanosheets directly grown on nickel foam through a simple hydrothermal method. Characterizations indicated that the Co3O4 nanosheets are completely and uniformly wrapped onto the surface of nickel foam to form a three-dimensional heterostructure. The resulting self-standing electrochemical electrode presents a high performance for the non-enzymatic detection of glucose, including short response time (<10 s), ultra-sensitivity (12.97 mA mM(-1) cm(-2)), excellent selectivity and low detection limit (0.058 μM, S/N = 3). These results indicate that Co3O4 nanosheets wrapped onto nickel foam are a low-cost, practical, and high performance electrochemical electrode for bio sensing.
Nickel–cobalt binary hydroxide nanotubes were fabricated by a facile synthetic approach by using Cu2O nanowires as sacrificial templates. The surface morphology of the binary hydroxide nanotubes can be easily controlled by adjusting the molar ratio of Ni to Co. With increasing Co content, the surfaces of the nanotubes tend to form hierarchical nanoflakes. The obtained nanotubes with high specific surface area exhibit typical battery-like electrochemical behavior. Among them, Ni–Co hydroxide nanotubes with Ni:Co=48:52 showed outstanding electrochemical characteristics, with a specific capacity of 209.9 mAh g−1 at 1 Ag−1 and remarkable cycling stability with 84.4 % capacity retention after 10 000 cycles at 20 A g−1. With the advantages of their unique nanostructure and the synergistic effect of the two elements, the Ni–Co binary hydroxide nanotubes are expected to be effective potential cathode materials for hybrid supercapacitors.
Uniform NiS2 hollow nanoprisms have been controllably synthesized by a facial sacrificial template method including two-step refluxed reactions. The morphology of the hollow NiS2 prisms can be easily tailored by the low cost nickel complex template. With unique hollow structure, efficient electron, and ion transport pathway as well as single crystal structure, the NiS2 hollow prisms electrode exhibits excellent pseudocapacitive performance in LiOH electrolyte. It can deliver a specific capacitance of 1725 F g–1 at a current density of 5 A g–1 and 1193 F g–1 even at a current density of 40 A g–1. Furthermore, the materials also present an amazing cycling stability, that is, the specific capacitance can increase from 1367 F g–1 to 1680 F g–1 after 10 000 cycles of charge–discharge at the current density of 20 A g–1.
Abstract A facile and simple method is developed to synthesize putty‐like MnO 2 /carbon nanotube (CNT) nanostructured composite which shows promising performance as the anode for lithium‐ion batteries (LIBs). The interwoven structure between CNTs and MnO 2 enables excellent putty‐like processability, which can be easily molded to various shapes or rolled to a flexible film with different thickness. Furthermore, the morphology and structure of the composite can be easily controlled by adjusting the mass ratio of MnO 2 to CNT. Serving as anode materials in LIBs, a high‐specific capacity of 796 mAh g −1 is achieved at a current density of 500 mA g −1 with a potential window from 0 to 3.0 V. And a specific capacity of 236 mA h g −1 is maintained even at a high current density of 10 A g −1 . The high‐specific capacity and outstanding high‐rate performance of the material are attributed to the layered structure with unimpeded Li ions diffusion channels, high electron transport efficiency from the interlayered CNTs, and the high stability and flexibility of the skeleton. This work provides an insight for the scalable preparation of novel electrode materials with both enhanced electrochemical performance and increased mechanical properties/flexibility for future multifunctional energy storage devices.
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