In situ fabrication of Ni(OH)2/Cu2O nanosheets on nanoporous NiCu alloy for high performance supercapacitor

Single-step,in-situfabrication of flower-like NiCuMn hybrid oxyhydroxide electrodes for enhanced supercapacitor performance

The rational design of highly active and low-cost electrode material is very promising for energy storage applications. The development of supercapacitors with high energy/power density is an imperative and challenging research objective. Herein, we report a highly facile synthesis approach for developing unique nano-porous hybrid NiCuMn oxyhydroxide architecture with remarkable electrochemical energy storage characteristics. The process involves dealloying of Ni15Cu15Mn70alloy in an oxygen rich environment, resulting in a uniform 3-dimensional flower like morphology. The dealloyed electrode demonstrates ultra-high specific capacitance of 4110 F cm-3at a high current density of 20 mA cm-2. A symmetric device exhibits a high volumetric capacitance of 365 F cm-3at a current density of 10 mA cm-2with a large potential window of 1.7 V. Even at very high-power density of 850 W l-1, the device exhibits a high energy density of 146 Wh l-1along with remarkable cyclic stability of 95.4% after 10 000 cycles. The superior performance of nano-porous hybrid NiCuMn oxyhydroxide architecture was attributed to its unique microstructure that provides high surface area, and marginal internal resistance ensuring rapid charge transport.

Emerging 2D Copper-Based Materials for Energy Storage and Conversion: A Review and Perspective

2D materials have shown great potential as electrode materials that determine the performance of a range of electrochemical energy technologies. Among these, 2D copper-based materials, such as Cu-O, Cu-S, Cu-Se, Cu-N, and Cu-P, have attracted tremendous research interest, because of the combination of remarkable properties, such as low cost, excellent chemical stability, facile fabrication, and significant electrochemical properties. Herein, the recent advances in the emerging 2D copper-based materials are summarized. A brief summary of the crystal structures and synthetic methods is started, and innovative strategies for improving electrochemical performances of 2D copper-based materials are described in detail through defect engineering, heterostructure construction, and surface functionalization. Furthermore, their state-of-the-art applications in electrochemical energy storage including supercapacitors (SCs), alkali (Li, Na, and K)-ion batteries, multivalent metal (Mg and Al)-ion batteries, and hybrid Mg/Li-ion batteries are described. In addition, the electrocatalysis applications of 2D copper-based materials in metal-air batteries, water-splitting, and CO₂ reduction reaction (CO₂ RR) are also discussed. This review also discusses the charge storage mechanisms of 2D copper-based materials by various advanced characterization techniques. The review with a perspective of the current challenges and research outlook of such 2D copper-based materials for high-performance energy storage and conversion applications is concluded.

Cu2O/CuS/ZnS Nanocomposite Boosts Blue LED-Light-Driven Photocatalytic Hydrogen Evolution

In the present work, we described the synthesis and characterization of the ternary Cu2O/CuS/ZnS nanocomposite using a facile two-step wet chemical method for blue LED-light-induced photocatalytic hydrogen production. The concentrations of the ZnS precursor and reaction time were essential in controlling the photocatalytic hydrogen production efficiency of the Cu2O/CuS/ZnS nanocomposite under blue LED light irradiation. The optimized Cu2O/CuS/ZnS nanocomposite exhibited a maximum photocatalytic hydrogen evolution rate of 1109 µmolh−1g−1, which was remarkably higher than Cu2O nanostructures. Through the cycle stability it can be observed that the hydrogen production rate of the Cu2O/CuS/ZnS nanocomposite decreased after 4 cycles (1 cycle = 3 h), but it remained at 82.2% of the initial performance under blue LED light irradiation. These reasons are mainly attributed to the introduction of CuS and ZnS to construct a rationally coupled reaction system, which enables the synergistic utilization of photogenerated carriers and the increased absorption of visible light for boosting blue LED-light-driven photocatalytic hydrogen evolution.

Synthesis of nickel-copper composite with controllable nanostructure through facile solvent control as positive electrode for high-performance supercapacitors

The surface characteristics of electrodes vary depending on the solvent used. Furthermore, electrochemical performance varies depending on the surface morphology of the electrode. In this study, we grew 3D binary NiCu-based composites on Ni foam, via a binder-free hydrothermal method, for use as a cathode in high-performance supercapacitors. We employed different solvents to prepare the electrodes by adjusting the ratio of deionized water (DI water) to methanol. The electrode prepared using DI water as the solvent had the largest surface area with a nanowire structure. This morphology allowed for good electrical performance by greatly improving the electrode and electrolyte contact area and shortening the ion diffusion path. The optimized deposition of NiCu(CO₃)(OH)₂ nanowires (50 mL of DI water as solvent) showed an excellent maximum specific capacity of 758.9 mA h g^-1 at a current density of 3 A g^-1, as well as outstanding cycling performance with 87.2% retention after 5000 cycles. In this work, we focused on the large specific surface area and suitable electrochemical properties of NiCu(CO₃)(OH)₂ electrodes with various solvents. As a result, the asymmetric supercapacitor (ASC) using the NiCu(CO₃)(OH)₂ electrode prepared with 50 ml of DI water as the solvent as the positive electrode and graphene as the negative electrode, exhibited an energy density of 26.7 W h kg^-1 at a power density of 2534 W kg^-1, and excellent cycling stability with 91.3% retention after 5000 cycles. The NiCu(CO₃)(OH)₂//graphene ASC could turn on an LED light and demonstrated better electrical performance than most previously reported nickel- and copper-based carbonate hydroxide ASCs. In addition, in the present scenario where many nanoscale studies are conducted, a method of controlling the nanostructure of a material through facile solvent control will be of great help to many researchers.

Hierarchical Ni(OH)2/Cu(OH)2 interwoven nanosheets in situ grown on Ni-Cu-P alloy plated cotton fabric for flexible high-performance energy storage

Flexible energy storage electrodes with high conductivity and capacity are crucial for wearable electronic clothes. Herein, a flexible hierarchical Ni(OH)₂/Cu(OH)₂ interwoven nanosheets in situ coated on Ni-Cu-P alloy plated cotton fabric textile (NCO/CF), which displays perfect conductive and electrochemical performance, is prepared by electroless deposition and electrochemical oxidation method. While the Ni-Cu-P alloy layer coated on the fabric effectively contributes to excellent mechanical performance and electro-conductivity of the as-prepared NCO/CF electrode, the hierarchical Ni(OH)₂/Cu(OH)₂ interwoven nanosheets in the oxidation layer effectively lead to a high energy storage performance with a specific areal capacity of 4.7 C cm^-2 at a current density of 2 mA cm^-2. When the power density of the two-electrode system based on NCO/CF and the carbon cloth (CC) is 2.4 mW cm^-2, the energy density is 1.38 mW h cm^-2. Furthermore, the flexible solid-state energy storage f-NCO/CF//CC is assembled in a self-powered system and supplies continuous power for electronic devices, demonstrating that NCO/CF is promising to be applied in various energy storage devices to power portable and wearable devices in the future.

A Ni(OH)2 nanopetals network for high-performance supercapacitors synthesized by immersing Ni nanofoam in water

Developing a facile and environmentally friendly approach to the synthesis of nanostructured Ni(OH)₂ electrodes for high-performance supercapacitor applications is a great challenge. In this work, we report an extremely simple route to prepare a Ni(OH)₂ nanopetals network by immersing Ni nanofoam in water. A binder-free composite electrode, consisting of Ni(OH)₂ nanopetals network, Ni nanofoam interlayer and Ni-based metallic glass matrix (Ni(OH)₂/Ni-NF/MG) with sandwich structure and good flexibility, was designed and finally achieved. Microstructure and morphology of the Ni(OH)₂ nanopetals were characterized. It is found that the Ni(OH)₂ nanopetals interweave with each other and grow vertically on the surface of Ni nanofoam to form an "ion reservoir", which facilitates the ion diffusion in the electrode reaction. Electrochemical measurements show that the Ni(OH)₂/Ni-NF/MG electrode, after immersion in water for seven days, reveals a high volumetric capacitance of 966.4 F/cm³ at a current density of 0.5 A/cm³. The electrode immersed for five days exhibits an excellent cycling stability (83.7% of the initial capacity after 3000 cycles at a current density of 1 A/cm³). Furthermore, symmetric supercapacitor (SC) devices were assembled using ribbons immersed for seven days and showed a maximum volumetric energy density of ca. 32.7 mWh/cm³ at a power density of 0.8 W/cm³, and of 13.7 mWh/cm³ when the power density was increased to 2 W/cm³. The fully charged SC devices could light up a red LED. The work provides a new idea for the synthesis of nanostructured Ni(OH)₂ by a simple approach and ultra-low cost, which largely extends the prospect of commercial application in flexible or wearable devices.