Ultra-long life nickel nanowires@nickel-cobalt hydroxide nanoarrays composite pseudocapacitive electrode: Construction and activation mechanism

High mass loading NiCo-OH nanothorns coated CuO nanowire arrays for high-capacity nickel-zinc battery

The rational design of cathode materials with core-shell heterostructures is significant to develop a Ni//Zn battery with both high gravimetric and areal energy density under high mass loading. In this work, the NiCo-OH nanothorns with a mass loading of 11.6 mg cm^-2were coated on CuO nanowire arrays via a chemical bath deposition method. Thanks to the construction of 3D core-shell nanowire arrays and appropriate cobalt doping, as-fabricated Ni//Zn battery based on the NiCo-OH as cathode achieved the maximum specific capacity of 383 mAh g^-1at 5 mA cm^-2with high energy density of 649 Wh kg^-1at 0.73 kW kg^-1, indicating good energy storage performance in Ni//Zn battery.

Novel urchin-like FeCo oxide nanostructures supported carbon spheres as a highly sensitive sensor for hydrazine sensing application

Herein, we successfully fabricated a novel nanostructure based on hierarchical urchin-like FeCo oxide supported carbon spheres (FeCo Oxide/CSs) via a two-step hydrothermal method followed by a simple annealing step at 300 °C under air. It was found that such urchin-like FeCo Oxide/CSs structure exhibited superior catalytic activity towards hydrazine oxidation to CSs, Fe Oxide/CSs, Co Oxide/CSs, and FeCo Hydroxide/CSs material. In this regard, the FeCo Oxide/CSs displayed a wide linear detection range of 0.1-516.6 μM, low detection limit of 0.1 μM, and long-term stability. The material also showed good selectivity towards hydrazine detection in the presence of various interferences, such as uric acid, ascorbic acid, urea, dopamine, Na⁺, SO₄^2-, K⁺, and Cl-. The excellent sensing performance of the FeCo Oxide/CSs was assumed to the unique hierarchical urchin structure with the high density and uniformity of nano-sized FeCo Oxide nanoneedles, which produced massive electroactive sites and enhanced charge transfer ability. The achieved results implied that the FeCo Oxide/CSs may be a great candidate for sensitive hydrazine detection.

Controlled Hydrolysis of Metal-Organic Frameworks: Hierarchical Ni/Co-Layered Double Hydroxide Microspheres for High-Performance Supercapacitors

Pseudomorphic conversion of metal-organic frameworks (MOFs) enables the fabrication of nanomaterials with well-defined porosities and morphologies for enhanced performances. However, the commonly reported calcination strategy usually requires high temperature to pyrolyze MOF particles and often results in uncontrolled growth of nanomaterials. Herein, we report the controlled alkaline hydrolysis of MOFs to produce layered double hydroxide (LDH) while maintaining the porosity and morphology of MOF particles. The preformed trinuclear M₃(μ₃-OH) (M = Ni²⁺ and Co²⁺) clusters in MOFs were demonstrated to be critical for the pseudomorphic transformation process. An isotopic tracing experiment revealed that the ¹⁸O-labeled M₃(μ₃-¹⁸OH) participated in the structural assembly of LDH, which avoided the leaching of metal cations and the subsequent uncontrolled growth of hydroxides. The resulting LDHs maintain the spherical morphology of MOF templates and possess a hierarchical porous structure with high surface area (BET surface area up to 201 m²·g^-1), which is suitable for supercapacitor applications. As supercapacitor electrodes, the optimized LDH with the Ni:Co molar ratio of 7:3 shows a high specific capacitance (1652 F·g^-1 at 1 A·g^-1) and decent cycling performance, retaining almost 100% after 2000 cycles. Furthermore, the hydrolysis method allows the recycling of organic ligands and large-scale synthesis of LDH materials.

Ni(OH)2@Ni core-shell nanochains as low-cost high-rate performance electrode for energy storage applications

Energy storage performances of Ni-based electrodes rely mainly on the peculiar nanomaterial design. In this work, a novel and low-cost approach to fabricate a promising core-shell battery-like electrode is presented. Ni(OH)₂@Ni core-shell nanochains were obtained by an electrochemical oxidation of a 3D nanoporous Ni film grown by chemical bath deposition and thermal annealing. This innovative nanostructure demonstrated remarkable charge storage ability in terms of capacity (237 mAh g⁻¹ at 1 A g⁻¹) and rate capability (76% at 16 A g⁻¹, 32% at 64 A g⁻¹). The relationships between electrochemical properties and core-shell architecture were investigated and modelled. The high-conductivity Ni core provides low electrode resistance and excellent electron transport from Ni(OH)₂ shell to the current collector, resulting in improved capacity and rate capability. The reported preparation method and unique electrochemical behaviour of Ni(OH)₂@Ni core-shell nanochains show potential in many field, including hybrid supercapacitors, batteries, electrochemical (bio)sensing, gas sensing and photocatalysis.

Cu-Co-M arrays on Ni foam as monolithic structured catalysts for water splitting: effects of co-doped S-P

Finding new methods to design environmentally friendly, highly stable, and robust oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts remains an extremely important challenge and affords several opportunities for exploiting the water-splitting process. In our work, Cu-Co-M (M = O, S, P, Se, S-P, and P-S) materials were grown in situ on three-dimensional (3D) porous nickel foam (NF) with good electrical conductivity by hydrothermal synthesis, vulcanization, selenylation, and phosphorization of the Cu-Co-precursor under an Ar atmosphere. Cu-Co-P-S/NF presents an overpotential value of 220 mV at 50 mA cm-2 for OER and that for Cu-Co-P-S/NF of 120 mV at 10 mA cm-2 for HER in an alkaline medium. In addition, considering the superior activities of Cu-Co-P-S/NF for OER and HER, the electrode pairing of Cu-Co-P-SOER//Cu-Co-P-SHER is designed for overall water splitting, and the experimental result shows that only a cell voltage of 1.55 V is needed to obtain a current density of 20 mA cm-2. According to the literature, this cell voltage is also among the lowest values that have been previously reported for electrocatalytic water splitting. Further, Cu-Co-P-S//Cu-Co-P-S exhibited efficient stability during a 20 h durability test without significant attenuation under alkaline conditions. By using XPS spectroscopy characterization, it was shown that Cu-Co-P-S presented the highest catalytic performance and long-term durability owing to the abundance of Co3+. The novelty of selecting the highest activity with the same catalyst for OER and HER from Cu-Co-M (M = O, S, P, Se, S-P, and P-S) in order to obtain a well-matched electrode pair, and therefore, simplifying the water-splitting device affords a wide range of possibilities for further exploitation of environmentally friendly and highly efficient electrode pairs.

Three-dimensional cotton-like nickel nanowire@Ni-Co hydroxide nanosheet arrays as binder-free electrode for high-performance asymmetric supercapacitor

Three-dimensional (3D) cotton-like Ni-Co layered double hydroxide nanosheet arrays/nickel nanowires (3D Ni-Co LDH/NiNw) were successfully fabricated through a facile chemical bath deposition method. The 3D nickel nanowires are used as a conductive substrate with robust adhesion for high-pseudocapacitance Ni-Co LDH. The 3D Ni-Co LDH/NiNw electrode shows a high areal specific capacitance of 14 F cm^-2 at 5 mA cm^-2 and quality specific capacitance of 466.6 F g^-1 at 0.125 A g^-1 with respect to the whole quality of the electrode. The fabricated asymmetric supercapacitor exhibits a remarkable energy density of 0.387 mWh cm^-2 using Ni-Co LDH/NiNw as the negative electrode. This high-performance composite electrode presents a new and affordable general approach for supercapacitors.