Changhui Wang

One-Step Electrophoretic Deposition of Reduced Graphene Oxide and Ni(OH)2 Composite Films for Controlled Syntheses Supercapacitor Electrodes

A facile, rapid, scalable, and environmentally friendly electrophoretic deposition (EPD) approach has been developed for the fabrication of reduced graphene oxide (RGO) and Ni(OH)(2) syntheses based on EPD of graphene oxide (GO) and Ni(NO(3))(2) colloidal suspension. Nickel ion decoration made GO positively charged and further made cathodic EPD feasible. Direct assembly by one-step EPD facilitated transformation from GO to RGO and resulted in multilayer or flower-like RGO/Ni(OH)(2) hybrid films on different substrates. X-ray diffraction analysis suggested that the crystal structures of Ni(OH)(2) depended on the colloidal suspension and the substrate. Further transmission electron microscopy characterization indicated that Ni(OH)(2) nanoclusters composed of 5-10 nm nanoparticles in grain size were homogeneously dispersed and anchored on the RGO. The resulting 100% binder-free RGO/Ni(OH)(2) electrodes exhibited excellent pseudocapacitive behavior with high specific capacitance of 1404 F g(-1) at 2 A g(-1), high rate capability, and good electrochemical cyclic stability. These results paved the way for EPD to produce RGO-based nanocomposite films for high-performance energy storage devices.

Ethylene Glycol Intercalated Cobalt/Nickel Layered Double Hydroxide Nanosheet Assemblies with Ultrahigh Specific Capacitance: Structural Design and Green Synthesis for Advanced Electrochemical Storage

Because of the rapid depletion of fossil fuels and severe environmental pollution, more advanced energy-storage systems need to possess dramatically improved performance and be produced on a large scale with high efficiency while maintaining low-enough costs to ensure the higher and wider requirements. A facile, energy-saving process was successfully adopted for the synthesis of ethylene glycol intercalated cobalt/nickel layered double hydroxide (EG-Co/Ni LDH) nanosheet assembly variants with higher interlayer distance and tunable transitional-metal composition. At an optimized starting Co/Ni ratio of 1, the nanosheet assemblies display a three-dimensional, spongelike network, affording a high specific surface area with advantageous mesopore structure in 2-5 nm containing large numbers of about 1.2 nm micropores for promoting electrochemical reaction. An unprecedented electrochemical performance was achieved, with a specific capacitance of 4160 F g(-1) at a discharge current density of 1 A g(-1) and of 1313 F g(-1) even at 50 A g(-1), as well as excellent cycling ability. The design and optimization of EG-Co/Ni LDH nanosheets in compositions, structures, and performances, in conjunction with the easy and relatively green synthetic process, will play a pivotal role in meeting the needs of large-scale manufacture and widespread application for advanced electrochemical storage.

Large-Scale Production of Nanographene Sheets with a Controlled Mesoporous Architecture as High-Performance Electrochemical Electrode Materials

Graphene is considered as a rising-star material because of its unique properties and it is a promising material for applications in many fields. In recent years, experiments on graphene fabricated by using versatile methods have shed light on the crucial problem of aggregation and restacking, which is induced by strong π-π stacking and van der Waals forces, but preparation methods for real-world applications are still a great challenge. Here we report a facile, rapid, and environmentally friendly process, the burn-quench method, that allows large-scale and controlled synthesis of ordered mesoporous nanographene with 1-5 layers, which has a high surface area and electric conductivity. Electrodes composed of nanographene with a mesoporous architecture used both in electrochemical capacitors and lithium-ion batteries have a high specific capacitance, rate capability, energy density, and cyclic stability. Our results represent an important step toward large-scale graphene synthesis based on this new burn-quench method for applications in high-performance electrochemical energy storage devices.

Facile fabrication of nanostructured NiCo2O4 supported on Ni foam for high performance electrochemical energy storage

Intensive research in the area of electrochemical energy storage (EES) in the past decade has been inspired by the demand for EES in handheld electronic devices, transportation, and storage of renewable energy for the power grid. It has become necessary to find novel electrode materials with high performance, low cost and advanced electrode architecture to meet the large-scale commercial applications of EES. We developed a facile, green and energy-saving technique to fabricate cost-effective nanostructured NiCo2O4 supported on Ni foam (NiCo2O4/Ni foam) with a unique microstructure. As a binder-free electrode material, a high specific capacitance of 760 F g−1 was achieved with excellent cyclability at a current density of 1 A g−1. In conjunction with the superior electrode architecture, the nanoplate-like NiCo2O4/Ni foam with optimal performance has the potential to meet the needs of its wide commercial application for high-efficiency EES. The preparation method may be extended to other metal oxide/hydroxide-based materials with outstanding nanostructures for electronic, magnetic, optical, photochemical, and catalytic applications.