CoNi2 S4 Electrode with High Mass-Loading for High-Energy-Density Supercapacitor: Role of S-Containing Anions Exchange.

Anion exchange is recognized as an effective method to regulate the composition, electronic conductivity, and electrochemical behavior of the transition metal-based compounds. In this work, anion exchange is adopted as a rational post-treatment route to facilitate the capacitive activity of CoNi2 S4 nanoparticle arrays grown on carbon cloth (CC) with high mass-loading. As soaked in saturated Na2 S solution, the CoNi2 S4 /CC electrode showed an increased capacity from 483 C g-1 to 841 C g-1 at 10 mA cm-2 with excellent rate performance and stable cycling performance, which was superior to the CoNi2 S4 /CC electrode activated by NaBH4 reduction. Anion exchange was beneficial for enhancing the crystallinity, retaining the adhesion of nanoarrays, and realizing low resistance nature in a mild route. The as-assembled CoNi2 S4 /CC//activated CC hybrid supercapacitor delivered a high areal capacitance of 1.28 F cm-2 at 5 mA cm-2 , and achieved an energy density of 0.58 mWh cm-2 at a power density of 4.5 mW cm-2 with excellent cycle stability with 90.6 % capacity retention after 10000 cycles.

[Comparison of multislice spiral CT and MRI in diagnosis of occult fracture of knee joint with meniscus and ligament injury].

OBJECTIVE: To investigate the diagnostic value of multislice spiral CT (MSCT) and MRI in occult fracture of knee joint with meniscus and ligament injury. METHODS: From January 2020 to March 2021, 63 patients with knee occult fracture with meniscus and ligament injury, including 41 males and 22 females, aged from 21 to 67 years old, with an average of (44.35±8.77) years old, the course of disease ranged from 1 to 6 days, with an average of (4.64±1.75) days, the body mass index (BMI) was (19.85±2.78) kg/m2. MSCT and MRI data of 63 patients were collected and statistically analyzed to evaluage their diagnist value. RESULTS: The detection of MRI for occult knee fravtures with meniscus and ligament injury, joint cavity effusion, bone marrow edema, and articular surface injury were 100.00% (63/63), 95.24% (60/63), 42.86% (27/63) and 36.51% (23/63), respectively. The detection rates of MSCT were 49.21% (31/63), 41.27% (26/63), 0.00% (0/63) and 1.59% (1/63), respectively, significantly lwver than that of MRI (P<0.05). The diagnostic sensitivity, specificity and accuracy of MRI were significantly higher than those of MSCT(P<0.05). CONCLUSION: The sensitivity, specificity and accuracy of magnetic resonance imaging in the diagnosis of occult fracture of knee joint with meniscus and ligament injury are significantly better than that of MSCT. MRI has higher accuracy in the diagnosis of peripheral tissue diseases such as joint cavity, articular surface and bone marrow, and can reduce the risk of clinical misdiagnosis.

Quasi-Parallel NiFe Layered Double Hydroxide Nanosheet Arrays for Large-Current-Density Oxygen Evolution Electrocatalysis.

Designing advanced electrocatalysts for oxygen evolution at large current density (>500 mA cm-2 ) is critical to practical water splitting applications. Herein, a novel quasi-parallel NiFe layered double hydroxide (NiFe LDH) nanosheet arrays with pattern alignment on Ni foam was developed. The initial α-Ni(OH)2 layer induced effective coprecipitation between Ni2+ and Fe3+ for the formation of LDH phase, guaranteeing the electronic pulling effect among metal cations and enhancing the interaction between active materials and substrate for excellent adhesion and electrical conductivity. Quasi-parallel NiFe LDH nanoarrays exhibited outstanding oxygen evolution activity with a small Tafel slope of 30.1 mV dec-1 and overpotentials of 196, 255, and 284 mV at a current density of 10, 500, and 1000 mA cm-2 in 1.0 m KOH solution, respectively, and high stability over 40 h at 750 mA cm-2 . This work presents a new strategy towards fabricating electrode materials with exceptional performance.

Anion Exchange of Ni-Co Layered Double Hydroxide (LDH) Nanoarrays for a High-Capacitance Supercapacitor Electrode: A Comparison of Alkali Anion Exchange and Sulfuration.

A facile and new anion exchange process is presented, which involves the conversion of NiCo-CO3 layered double hydroxide (LDH) nanosheet arrays in an alkaline solution. The anion exchange between CO3 2- and OH- results in the construction of a reservoir for OH- anions, and the decoration of thin nanoflakes on the surface of nanosheets effectively enlarges the surface area of NiCo LDH nanoarrays. The capacitance of the as-soaked NiCo LDH nanoarrays electrode increases from 1.78 F cm-2 (684 F g-1 ) to 6.22 F cm-2 (2391 F g-1 ) at 2 mA cm-2 after soaking for 12 h. Moreover, the soaked NiCo-OH LDH electrode exhibits an enhanced rate capacity, high coulombic efficiency, and good cycling stability compared with the Ni-Co-S nanosheet electrode synthesized through a hydrothermal sulfuration process. The as-assembled all-solid-state NiCo LDH//active carbon asymmetric supercapacitor shows a maximum energy density of 83.4 W h kg-1 at a power density of 1066 W kg-1 .

In situ fabrication of Ni-Co (oxy)hydroxide nanowire-supported nanoflake arrays and their application in supercapacitors.

Three-dimensional (3D) hybrid nanostructured arrays grown on a flexible substrate have recently attracted great attention owing to their potential application as supercapacitor electrodes in portable and wearable electronic devices. Here, we report an in situ conversion of Ni-Co active electrode materials for the fabrication of high-performance electrodes. Ni-Co carbonate hydroxide nanowire arrays on carbon cloth were initially synthesized via a hydrothermal method, and they were gradually converted to Ni-Co (oxy)hydroxide nanowire-supported nanoflake arrays after soaking in an alkaline solution. The evolution of the supercapacitor performance of the soaked electrode was investigated in detail. The areal capacitance increases from 281 mF cm-2 at 1 mA cm-2 to 3710 and 3900 mF cm-2 after soaking for 36 h and 48 h, respectively. More interestingly, the electrode also shows an increased capacitance with charge/discharge cycles due to the long-time soaking in KOH solution, suggesting novel cycling durability. The enhancement in capacitive performance should be related to the formation of a unique nanowire-supported nanoflake array architecture, which controls the agglomeration of nanoflakes, making them fully activated. As a result, the facile in situ fabrication of the hybrid architectural design in this study provides a new approach to fabricate high-performance Ni/Co based hydroxide nanostructure arrays for next-generation energy storage devices.

Enhanced supercapacitor performance of Mn3O4 nanocrystals by doping transition-metal ions.

Pristine and transition-metal-doped Mn3O4 nanocrystals shaped in octahedrons have been synthesized by hydrothermal reduction of potassium permanganate and characterized by SEM/TEM, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical experiments. The results reveal that a multistep reduction process is taking place, and the introduction of doping ions causes a direct synthesis of single-phase Mn3O4 nanocrystals. To assess the properties of Mn3O4 nanocrystals for their use in supercapacitors, cyclic voltammetry and galvanostatic charging-discharging measurements are performed. The phase stability during cycling and charge-transfer behavior are greatly improved by doping with transition metal, and Cr-doped Mn3O4 nanocrystals exhibit a maximum specific capacitance of 272 F g(-1) at a current density of 0.5 A g(-1). These doped Mn3O4 nanocrystals could be a promising candidate material for high-capacity, low-cost, and environmentally friendly electrodes for supercapacitors. In addition, these results have verified the ability of doping to improve capacitive performances of spinel-structured transition-metal oxides.