Ni-Co Double Hydroxide Research Articles

Ultrathin Ni-Co double hydroxide nanosheets with conformal graphene coating for highly active oxygen evolution reaction and lithium ion battery anode materials

Ultrathin graphene wrapped Ni-Co double hydroxide nanosheets (∼10nm) were synthesized by a facile and rapid electrodeposition process, and evaluated as electrocatalysts for oxygen evolution reaction (OER) and anode materials for Li-ion batteries. The conformal graphene coating on the nanosheets significantly increased the conductivity and surface area of the Ni-Co double hydroxide electrodes. As the OER electrocatalyst, the Ni-Co graphene hybrids show a superior catalytic activity with a small Tafel slope of 67mV per decade due to the synergy between the abundant active sites of the Ni-Co hydroxides and the conductive graphene coating, and a modest overpotential of 280mV at a current density of 10mAcm−2. Impressively, the electrodes exhibit an excellent stability evaluated by chronopotentiometry under a high current density of 30mAcm−2 for 12h. As Li-ion battery anode, the materials show a high specific capacity of 373mAhg−1 up to 500 cycles even at a high current density of 1000mAg−1. This study provides a new strategy to develop robust and affordable alternative OER catalyst and anode material for high-performance lithium ion batteries.

Ternary Ni-Co-Mo oxy-hydroxide nanoflakes grown on carbon cloth for excellent supercapacitor electrodes

Ternary Ni-Co-Mo oxy-hydroxide nanoflakes grown on carbon cloth was successfully fabricated based on a facile hydrothermal method. This composite product consists of three components: Ni-Co double hydroxide and Mo oxide. As a novel electrode material for pseudocapacitors, the Ni-Co-Mo oxy-hydroxide nanoflakes on carbon cloth exhibit excellent electrochemical properties, with a specific capacitance of 2562Fg−1 at 1Ag−1, and a good cycling stability. The excellent electrochemical performance can be attributed to the large specific surface area and the enhanced conductivity achieved through incorporating of Mo. By virtue of simple fabrication procedures and enhanced electrochemical performance, such ternary oxy-hydroxide nanoflakes have highly promising potential for energy storage devices.

High-stable α-phase NiCo double hydroxide microspheres via microwave synthesis for supercapacitor electrode materials

Fast and low-cost fabrication of high performance electrode materials is of great importance for the application of supercapacitors. Herein, in our research, three-dimensional (3D) flower-like NiCo double hydroxide (NiCo DH) microsphere was successfully synthesized via a rapid, inexpensive and energy-saving microwave route without using any template or surfactant under atmospheric pressure. The as-obtained NiCo DH microsphere endowed with α-phase structure with CNO− ions intercalation in the interlayers (7.3Å) was composed of ultrathin nanosheets with thickness less than 10nm. Electrochemical test revealed the NiCo DH electrode showed a high specific capacitance of 1120Fg−1 at 1Ag−1 and remained 996Fg−1 at 10Ag−1 (88.9% retention). Moreover, after 2000 cycles, the capacitance reached 122.5% of its initial value at 10Ag−1 and still retained 93.8% at 30Ag−1 after another 1000 cycles, showing superb stability compared with reported α-phase hydroxides. The admirable stability could be attributed to the synergistic effect between Ni and Co elements, the ion exchange phenomenon between CNO− and OH− ions in the interlayer of NiCo DH during cycling test, and the coherent 3D superstructure. Besides, the asymmetric supercapacitor, with NiCo DH as positive electrode and activated carbon from coal as negative electrode, delivered a superior energy density of 42.5Whkg−1. Consequently, the pleasant synthesis procedure and excellent integrated performance of NiCo DH enable it to be a promising electrode material for the energy storage devices.

Alternating Voltage Introduced NiCo Double Hydroxide Layered Nanoflakes for an Asymmetric Supercapacitor.

An electrochemical alternating voltage approach of producing NiCo double hydroxide (NiCoDH) layered ultrathin nanoflakes with large specific surface area (355.8 m(2) g(-1)), remarkable specific capacitance and rate capability is presented. The obtained NiCoDH as anode for asymmetric supercapacitors shows excellent energy density of 17.5 Wh kg(-1) at high power density of 10.5 kW kg(-1) and cycling stability (91.2% after 10,000 cycles).

One-pot microwave-assisted synthesis of reduced graphene oxide/nickel cobalt double hydroxide composites and their electrochemical behavior

Reduced graphene oxide (RGO)/nickel cobalt (NiCo) double hydroxide composites were synthesized by one-pot microwave-assisted method in propylene carbonate. This method is efficient because the reduction of graphene oxide and the formation of hydroxide particles on the graphene sheets were simultaneously produced. We investigated an effect of microwave irradiation in organic solvent and an electrochemical influence of nickel and cobalt ratio in double hydroxide. Morphological characterization was performed by XRD, FTIR, XPS and FE-SEM. It was found that the NiCo double hydroxide particles were well decorated on the surface of RGO sheets and the reduction of graphene oxide was completed by short-term microwave irradiation. Electrochemical behavior was also measured by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge performance. The highest specific capacitance was 1622Fg−1 obtained at (RGO)/NiCo 2:1 (weight ratio of nickel to cobalt was 2–1). Furthermore, the composites showed higher capacitance, as well as lower resistance, better rate capability and longer cycle life rather than RGO/Ni(OH)2 and RGO/Co(OH)2.

Nickel-Cobalt Double Hydroxide Decorated Carbon Nanotubes via Aqueous Electrophoretic Deposition towards Catalytic Glucose Detection

In this work, we present a facile technique based on electrophoretic deposition (EPD) to produce transition metal hydroxide decorated carbon nanotubes (CNT) for electrochemical applications. We specifically explore the performance of nickel-cobalt hydroxides given their high activity, conductivity and stability as compared to the individual hydroxides. We exploit the high local pH at the negative electrodes during water-based EPD to form nanoparticles of nickel-cobalt hydroxides in situ on the CNT surface. We focus our work here on obtaining functional and conductive deposits on CNTs. The hydrophilic binderless deposits of Ni-Co double hydroxide decorated CNTs obtained here are used for non-enzymatic glucose detection. XPS data and electrochemical testing reveal difference in the deposited double hydroxide based on chronology of charging salt addition even at the same ratio. When cobalt and nickel salts are sequentially added at a ratio of 1:1, the deposited double hydroxides show excellent glucose sensitivity of ~3300μA/mM.cm2 at applied potential of 0.55V vs. Ag/AgCl reference electrode.

Electrochemistry: Efficient Electrocatalytic Water Oxidation by Using Amorphous Ni–Co Double Hydroxides Nanocages (Adv. Energy Mater. 10/2015)

The feasibility of amorphous hollow Ni-Co double hydroxide nanomaterials for efficient electrochemical water oxidation is verified by Zhiyong Tang, Lin Guo, and co-workers in article number 1401880. The high catalytic activity and excellent stability of the NiCo2.7(OH)x nanocages demonstrate the promising application of amorphous nanomaterials in water electrochemical oxidation. Furthermore, the relation between the compositions of amorphous catalysts and their electrocatalytic activity is studied using experimental investigations and computational simulations.