Cai-Ling Xu

Electrodeposited nickel hydroxide on nickel foam with ultrahigh capacitance.

Electrodeposited Ni(OH)(2) on nickel foam with porous and 3D nanostructures has ultrahigh capacitance in the potential range -0.05-0.45 V, and a maximum specific capacitance as high as 3152 F g(-1) can be achieved in 3% KOH solution at a charge/discharge current density of 4 A g(-1).

3D Ni3S2 nanosheet arrays supported on Ni foam for high-performance supercapacitor and non-enzymatic glucose detection

3D Ni3S2 nanosheet arrays grown on Ni foam were successfully synthesized through a facile one-step hydrothermal approach and then directly applied as the electrode for a high-performance supercapacitor and non-enzymatic glucose sensor. The structure and morphology of the prepared Ni3S2 were characterized by X-ray power diffraction (XRD), field emission scanning electronic microscopy (FESEM) and transmission electron microscopy (TEM). The subsequent electrochemical measurements showed that the Ni3S2 nanosheet array electrode possessed a superior specific capacitance of 1370.4 F g−1 at a current density of 2 A g−1. Remarkably, a specific capacitance of 952.0 F g−1 could be still achieved at a high current density of 20 A g−1, indicating its excellent rate capability. And 91.4% of the specific capacitance was retained after 1000 cycles at a current density of 6 A g−1. Besides, to demonstrate its practical application, an asymmetric supercapacitor based on the Ni3S2 nanosheet array electrode as the positive electrode and activated carbon as the negative electrode was assembled. It delivered high energy density and good long-term stability. Additionally, serving as a non-enzymatic sensor, the 3D Ni3S2 nanosheet array electrode exhibited remarkable electrocatalytic activity towards glucose oxidation with a high sensitivity of 6148.0 μA mM−1 cm−2. All these impressive performances suggest that the Ni3S2 nanosheet array is a promising electrode material for supercapacitors and non-enzymatic glucose sensors.

Surfactant dependent self-organization of Co3O4 nanowires on Ni foam for high performance supercapacitors: from nanowire microspheres to nanowire paddy fields

Different surfactants were used in a typical hydrothermal process for controlling the morphology of the Co3O4 nanowire superstructure on Ni foam. It is easy for the Co3O4 nanowires to self-organize into nanowire microspheres on Ni foam in the absence of surfactants. And the nanowire microspheres gradually unfold into nanowire paddy fields with the addition of nonionic, cationic and anionic surfactants, respectively. The results of BET and electrochemical measurements show that the specific surface area and capacitance first decrease and then increase with the change in the Co3O4 superstructure morphology. Among these electrodes, the Co3O4 electrode with paddy like nanowires shows an outstanding specific capacitance of 1217.4 F g(-1) and areal specific capacitance as high as 6087 mF cm(-2) at 0.7 A g(-1) with high mass loading (5 mg cm(-2)), good power capability (showing a high specific capacitance of 835.1 F g(-1) (4176 mF cm(-2)) at 5 A g(-1)), excellent cycling stability and high columbic efficiency (∼100%). This exceptional performance is benefited from the almost monodispersed nanowire morphology and high specific surface area (121.4 m(2) g(-1)). At the same time, the asymmetric supercapacitor, employing the Co3O4 electrode with paddy-like nanowires as the positive electrode and the activated carbon electrode as the negative electrode, was successfully assembled. It shows a high specific energy and good long-term electrochemical stability. All these impressive results demonstrate that the Co3O4 electrode with paddy-like nanowires is promising for practical applications in supercapacitors.

Mesoporous nanowire array architecture of manganese dioxide for electrochemical capacitor applications.

Mesoporous MnO(2) nanowire array architecture exhibits enhanced capacitive and charge/discharge performance for electrochemical capacitors.

A highly sensitive non-enzymatic glucose sensor based on bimetallic Cu–Ag superstructures

Bimetallic Cu-Ag superstructures were successfully fabricated for the first time by using the natural leaves as reducing agent through a facile one-step hydrothermal process. Morphology, structure and composition of the Cu-Ag superstructures were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES), respectively. The results reveal that the Cu-Ag superstructure is bimetallic nanocomposite constructed by nanoparticles with low Ag content and shows a rough surface and porous flexural algae-like microstructure. By using a three-dimensional nickel foam as the scaffold, a novel non-enzymatic glucose sensor based on Cu-Ag nanocomposites has been fabricated and applied to non-enzymatic glucose detection. The as-prepared Cu-Ag nanocomposites based glucose sensor displays distinctly enhanced electrocatalytic activity compared to those obtained with pure Cu nanomaterials prepared with a similar procedure, revealing a synergistic effect of the matrix Cu and the doped Ag. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy indicate that the Cu-Ag superstructures based glucose sensor displays a fascinating sensitivity up to 7745.7 μA mM(-1) cm(-2), outstanding detection limit of 0.08 μM and fast amperometric response (<2 s) for glucose detection. Furthermore, the sensor also exhibits significant selectivity, excellent stability and reproducibility, as well as attractive feasibility for real sample analysis. Because of its excellent electrochemical performance, low cost and easy preparation, this novel electrode material is a promising candidate in the development of non-enzymatic glucose sensor.

Effect of electrodeposition temperature on the electrochemical performance of a Ni(OH)2 electrode

The effect of the electrodeposition temperature on the electrochemical performance of Ni(OH)2 electrode was investigated in this report. Ni(OH)2 was electrodeposited directly on nickel foam at different temperatures. The crystalline structure, morphology and specific surface area of the prepared Ni(OH)2 were characterized by X-ray powder diffraction (XRD), field emission scanning electronic microscopy (FESEM) and Brunauer–Emmett–Teller (BET). Electrochemical techniques such as cyclic voltammetry (CV), chronopotentiometry, and electrochemical impedance spectra (EIS) were carried out to systematically study the electrochemical performance of various Ni(OH)2 electrodes in 1 M KOH electrolyte. The results demonstrated that the electrodeposition temperature had obviously affected the properties of the Ni(OH)2. A pure α-Ni(OH)2 phase could be observed at low temperature. When the temperature increased to 65 °C, the β-Ni(OH)2 phase together with α-Ni(OH)2 phase were present. Moreover, the sample synthesized at 65 °C possessed a porous honeycomb-like microstructure and the corresponding specific capacitance was up to 3357 F g−1 at a charge–discharge current density of 4 A g−1, which suggested its potential application as an electrode material for supercapacitors.

Pt@UiO-66 heterostructures for highly selective detection of hydrogen peroxide with an extended linear range.

In this study, a good core-shell heterostructure of Pt NPs@UiO-66 was fabricated by encapsulating presynthesized platinum nanoparticles (Pt NPs) into the host matrix of UiO-66 which possesses the slender triangular windows with a diameter of 6 Å. The transmission electron microscopy images exhibited that the number of the encapsulated Pt NPs and the crystalline morphology of as-synthesized core-shell heterostructure samples had a series of changes with increasing the volume of the injected Pt NPs precursor solution. Among these samples, the Pt NPs@UiO-66-2 sample had a good crystalline morphology with several well-dispersed Pt NPs encapsulated in UiO-66 frameworks. But there were no obvious Pt NPs observed in the Pt NPs@UiO-66-1 sample, and for the Pt NPs@UiO-66-3 sample, the number of Pt NPs encapsulated in UiO-66 matrix notably reduced and the metal organic framework (MOF) crystals became small and aggregated. The electrochemical measurements showed that the Pt NPs@UiO-66-2 sample modified glass carbon electrode (GCE) presented a remarkable electrocatalytic activity toward hydrogen peroxide (H2O2) oxidation, including an excellent anti-interference performance even if the concentration of the interference species was the same as the H2O2, an extended linear range from 5 μM to 14.75 mM, a low detection limit, as well as good stability and reproducibility. The results indicate the superiority of MOFs in H2O2 detection. And more importantly, it will provide a new opportunity to promote the anti-interference performance of the nonenzyme electrochemical sensors.

Ni/CdS Bifunctional Ti@TiO2 Core-Shell Nanowire Electrode for High-Performance Nonenzymatic Glucose Sensing

In this work, a Ni/CdS bifunctional Ti@TiO2 core-shell nanowire electrode with excellent electrochemical sensing property was successfully constructed through a hydrothermal and electrodeposition method. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were employed to confirm the synthesis and characterize the morphology of the as-prepared samples. The results revealed that the CdS layer between Ni and TiO2 plays an important role in the uniform nucleation and the following growth of highly dispersive Ni nanoparticle on the Ti@TiO2 core-shell nanowire surface. The bifunctional nanostructured electrode was applied to construct an electrochemical nonenzymatic sensor for the reliable detection of glucose. Under optimized conditions, this nonenzymatic glucose sensor displayed a high sensitivity up to 1136.67 μA mM(-1) cm(-2), a wider liner range of 0.005-12 mM, and a lower detection limit of 0.35 μM for glucose oxidation. The high dispersity of Ni nanoparticles, combined with the anti-poisoning faculty against the intermediate derived from the self-cleaning ability of CdS under the photoexcitation, was considered to be responsible for these enhanced electrochemical performances. Importantly, favorable reproducibility and long-term performance were also obtained thanks to the robust frameworks. All these results indicate this novel electrode is a promising candidate for nonenzymatic glucose sensing.

High performance asymmetric supercapacitor based on MnO2 electrode in ionic liquid electrolyte

In this work, the electrochemical properties of a MnO2 nanocomposite electrode were investigated in 1-butyl-3-methyl-imidazolium hexafluorophosphate ([Bmim]PF6)/N,N-dimethylformamide (DMF) electrolyte. The [Bmim]PF6/DMF electrolyte with different volume fractions exhibits significant influence on the electrochemical properties of the electrode. When the volume ratio of [Bmim]PF6 and DMF was 1 : 1, the electrode showed the best electrochemical performance. The operation potential window of the MnO2 nanocomposite electrode in ionic liquids was 2.1 V and the specific capacitance according to the mass of MnO2 was 523.3 F g−1 at 3 A g−1. Then, a high-voltage (3 V) MnO2 asymmetric supercapacitor was successfully fabricated, using the MnO2 nanocomposite electrode, activated carbon and [Bmim]PF6/DMF as the positive electrode, negative electrode and electrolyte, respectively. The MnO2 asymmetric supercapacitor displayed a maximum specific energy of 67.5 W h kg−1 at a specific power of 593.8 W kg−1 and a maximum specific power of 20.4 kW kg−1 at a specific energy of 8.5 W h kg−1. The impressive results showed that [Bmim]PF6/DMF could be a promising electrolyte for MnO2 supercapacitors.

Reticular-vein-like Cu@Cu2O/reduced graphene oxide nanocomposites for a non-enzymatic glucose sensor

In this work, reticular-vein-like Cu@Cu2O/rGO nanocomposites have been synthesized by direct redox reaction of Cu and graphene oxide (GO) through a hydrothermal method where the macropore Cu sheets served as the precursor of reticular-vein-like Cu2O as well as the reducing agent of GO. FESEM and TEM were employed to characterize the morphology of the as-prepared samples. The results reveal that the reticular-vein-like Cu@Cu2O nanocomposites are homogeneously anchored onto rGO and act like the skeleton supporting the rGO sheets to avoid its aggregation or stacking. Electrochemical tests show that the Cu@Cu2O/rGO modified glassy carbon electrode (GCE) exhibits remarkable electrocatalytic activity towards glucose oxidation in both alkaline medium and human serum, including a wide linear range (0.005–7 mM), a low detection limit (0.5 μM), a rapid response (<2 s) as well as good stability and repeatability. More importantly, the interference from the commonly interfering species such as lactose, fructose, ascorbic acid (AA) and uric acid (UA) can be effectively avoided. All these results indicate this novel nanostructured material is a promising candidate for non-enzymatic glucose sensors.