Wencheng Hu

High-performance three-dimensional nanoporous NiO film as a supercapacitor electrode

A three-dimensional nanoporous NiO film was fabricated using a two-step process through an electrochemical route. The as-prepared NiO film exhibited a highly nanoporous structure and high surface area (264 m2 g−1). The textural characterization of the film and its electrochemical performance as an electrochemical electrode were investigated. The electrode showed a high specific capacitance (1776 F g−1), power density (89 Wh kg−1), and energy density (16.5 kW kg−1). In addition, the electrode exhibited high and stable specific capacitance retention after a long cycle test in KOH solution. More importantly, the power density met the power requirements of the Partnership for a New Generation of Vehicles (PNGV).

LaNiO3/NiO hollow nanofibers with mesoporous wall: a significant improvement in NiO electrodes for supercapacitors

Different molar ratios of La:Ni (LaNiO3/NiO) hollow nanofibers were prepared by electrospinning method. The morphologies and microstructures of the samples were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical properties of nanofibers were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) analyses in an aqueous electrolyte (7xa0M KOH). Results showed that adding the conductive material (LNO) can enhance the specific capacitance and electrochemical stability of the NiO nanofibers. In particular, La:Niu2009=u20091:2 (LNO:NiOu2009=u20091:1) showed a remarkable specific capacitance of 257.8xa0Fxa0g−1 scaled to the total mass of the electrode or 942xa0Fxa0g−1 scaled to the active mass (NiO) at a current density of 0.5xa0Axa0g−1. The cycling tests operated at a potential window of 0 to 0.45xa0V with a current density of 0.5xa0Axa0g−1 suggested that the electrode had excellent cycling performance, with only 10xa0% capacitance loss after 1000 cycles.

Mesoporous LaNiO3/NiO nanostructured thin films for high-performance supercapacitors

Mesoporous LaNiO3 (LNO)/NiO electrodes for thin film supercapacitors have been developed from a sol–gel precursor using polyethylene glycol 1000 (PEG 1000) as a template. It is the first time that the LNO/NiO thin films have been reported as electrochemical electrodes. Electrochemical measurements in an aqueous electrolyte (1 M Na2SO4) show areal specific capacitances of about 9.5 mF cm−2 and 1.85 mF cm−2 at the scan rates of 0.1 V s−1 and 100 V s−1, respectively. The film shows a quasi-rectangular curve even at the ultrahigh scan-rate of 100 V s−1, which is much higher than that of conventional supercapacitors. The specific capacitance is five orders of magnitude higher than most of the micro-/thin films. The cycling tests operated at the potential window of 0 to 1 V with a current density of 1 mA cm−2 suggest that the thin film electrode has an excellent cycling performance with only 2.8% capacitance loss after 1000 cycles. It is believed that LNO can improve the electrical conductivity and stability of the electrodes, and the porous structure can provide full accessibility of the electrolyte, which is helpful in enhancing the stable performance of the electrochemical behaviors.

Remarkable electrochemical properties of novel LaNi0.5Co0.5O3/0.333Co3O4 hollow spheres with a mesoporous shell

An atomization route incorporating colloidal silica as a template was employed to synthesize LaNi0.5Co0.5O3/0.333Co3O4 (LNCO/CO) hollow spheres with a highly mesoporous shell. XRD and FESEM and HRTEM were used to characterize the crystalline phases and micro-morphology, respectively. The mesoporous shell showed a high specific surface area of 247 m2 g−1 as well as a mean pore size of about 2.53 nm as determined from N2 adsorption–desorption isotherms. The as-obtained spherical hollow spheres exhibited remarkable electrochemical performance as a battery-type electrode material with a maximum specific capacity of 498C g−1 at a current density of 2 A g−1 and ultra-long charge–discharge stability for 50u2006000 cycles in a three-electrode system. Additionally, a hybrid supercapacitor assembled with LNCO/CO hollow spheres as the positive electrode and N-doped mesoporous carbon as the negative electrode showed a high specific capacitance of 113.2 F g−1 at 1 A g−1 and a very high energy density of 42.8 Wh kg−1 at a power density of 424 W kg−1. The hybrid supercapacitor also exhibited a long-term cycle life of up to 30u2006000 cycles with a specific capacitance retention of 90.4%, and these properties meet the growing demands of long-life energy-related devices.

Highly mesoporous structure nickel cobalt oxides with an ultra-high specific surface area for supercapacitor electrode materials

Highly mesoporous structure nickel cobalt oxides with an ultra-high specific surface area are synthesized through a sol–gel method by using silica derived from tetraethoxysilane hydrolysis as a template. The structural and morphological characteristics of the oxides are determined using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and N2 adsorption experiments. The electrochemical properties, including capacitance, of the oxides are analyzed through cyclic voltammetry, AC impedance spectroscopy, and charge–discharge tests in 7xa0M KOH under ambient conditions. The as-prepared nickel cobalt oxides possessing an ultra-high specific surface area of 438.3xa0m2xa0g−1 and a mesoporous structure exhibit a high specific capacitance of 1157.7xa0Fxa0g−1 and a long-term cyclic stability (97.13xa0% capacity retention after 5000xa0cycles). Thus, the prepared oxides are promising for supercapacitor applications.

High-boiling-point solvent synthesis of mesoporous NiCo2S4 with high specific surface area as supercapacitor electrode material

A facile synthesis approach was successfully developed to synthesize mesoporous NiCo2S4 in ethylene glycol. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and N2 adsorption–desorption experiment were conducted to examine the morphology and microstructure of the as-prepared NiCo2S4. Furthermore, electrochemical measurements, including cyclic voltammetry, galvanostatic charge–discharge tests, and electrochemical impedance spectroscopy, were carried out in a three-electrode system to evaluate the electrochemical properties of the mesoporous NiCo2S4. The as-prepared NiCo2S4 possessed a high specific surface area of 223.6xa0m2xa0g−1 with a high specific capacity of 406xa0Cxa0g−1 at 0.5xa0Axa0g−1. In addition, only a 6.3xa0% loss of specific capacity was observed at 5xa0Axa0g−1 after 20,000 GCD cycles, suggesting a long life cycle.

Mesoporous three dimension NiCo2O4/graphene composites fabricated by self-generated sacrificial template method for a greatly enhanced specific capacity

We reported a facile self-generated sacrificial template method for fabricating mesoporous three dimension NiCo2O4/graphene electrode material. Nickel, cobalt, and zinc ions dissolved in ethylene glycol reacted with potassium hydroxide solution to co-deposit onto graphene at 140u2009°C under atmospheric environment. With further addition of potassium hydroxide, zinc hydroxide as a self-generated sacrificial template was dissolved in situ, leading to the formation of mesoporous morphology. Structure and morphology characteristics were determined by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and N2 adsorption experiments. Electrochemical properties were analyzed by AC impedance spectroscopy, cycling voltammetry, and charge/discharge test in 2xa0M KOH. Results showed that the as—prepared NiCo2O4/graphene electrode possessed a large specific surface area of 281.4xa0m2xa0g−1, an ultrahigh specific capacity of 1024.99 and 662.12xa0Cxa0g−1 at current density of 1 and 50xa0Axa0g−1 respectively, and a long-term cycling life of 10,000 charge/discharge tests.

Porous Ag-doped MnO 2 thin films for supercapacitor electrodes

In this study, MnO2 was composited with different concentrations of Ag as dopant through a sol-gel method and deposited on the ITO glass substrates to form composite thin films. X-ray diffraction revealed the successful synthesis of crystalline structures while X-ray photoelectron spectroscopy showed the proper chemical compositional properties of MnO2 and elemental Ag. Field emission scanning electron microscopy was used to observe the cross-sectional features at the edge and mesoporosity on the surface. Different electrochemical measurements were carried out in the LiCl/PVA gel electrolyte to investigate the optimum amount of Ag dopant in composites to achieve good electrochemical properties for use as supercapacitor electrodes. The highest mass specific capacitance of 306xa0Fxa0g−1 was observed at an Ag dopant concentration of 7.5 at.% with a current density of 1xa0Axa0g−1. After 10,000 cycles, the capacitance decrease was less than 5% of the initial capacity and thus, exhibited a good long-term stability. The optimum concentration of Ag dopant and the mesoporous morphology were found to be of crucial importance in enhancing the electrical conductivity and the electrochemical performance of the MnO2 films.

Preparation of mesoporous La2NiO4/NiO filled activated carbon composite for high performance electrochemical electrodes

Active carbon (AC) is modified with nickel oxide (NiO) and inorganic metal oxide (La2NiO4) to synthesize the AC composites using a simple method. The different nanostructures of the obtained AC composites are investigated to achieve high specific capacitance and conductivity. The obtained composites are characterized via scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy. After two-time repeated immersion and heat treatment, the electrode material exhibits an AC-based mesoporous nanostructure. The corresponding resistance of the synthesized AC@NiO composite is 2.55xa0Ω, which is lower than that of pure AC (5.94xa0Ω). The CV results are obtained within a stable potential window of −0.9 to 0.9xa0V in 7xa0M KOH aqueous solution. The highest specific capacitance of the AC@NiO composite with La2NiO4 is 652.19xa0Fxa0g−1 at the scan rate of 1xa0mVxa0s−1.

Iron electroplating under hydrothermal conditions to improve anticorrosion performance

ABSTRACT Abundant research activities have been devoted to metal electroplating technology and hydrothermal fields. In this work, a hydrothermal method has been applied in metal electroplating for the first time, to the authors’ knowledge. Iron coatings that are electroplated under hydrothermal conditions yield numerous enhancements in various aspects, especially in anticorrosion applications. Electrochemical tests indicate that the corrosion resistance is significantly higher in iron coatings obtained under hydrothermal conditions than in those electroplated through the traditional method. Specifically, the coating resistance of the sample that was electroplated for 20u2005min at a current intensity of 300u2005mAu2005cm−2 and hydrothermal temperature of 120°C is up to 63.52u2005Ωu2005cm2, in a 3.5u2005wt-% NaCl solution at 25°C, which is approximately 44% larger than the resistance of the sample electroplated traditionally.