Rapid Synthesis of Nickel Hydroxide/Pt-Based Alloy Heterointerface for Hydrogen Evolution in Full pH Range

The huge application potential of nanoelectrocatalysts can become available only under the condition of scalable and reproducible preparation of nanomaterials (NMs). It is easily overlooked that most of the preparation methods for efficient platinum (Pt)-based electrocatalysts are complicated in process and time-/energy-consuming, which is not conducive to scalable and sustainable production. Herein, we propose a rapid and facile method to in situ construct a heterointerface between nickel hydroxide (Ni(OH)2) and NiPt alloy, in which the preparation steps are easy-to-operate and can be finished in 1 h. Furthermore, the ensemble effect between the Ni(OH)2 substrate and NiPt active sites benefits the water dissociation process in nonacidic conditions, while the electronic effect in NiPt contributes to the downshifted d-band center of Pt and the proper Gibbs free energy of hydrogen species. As a result, the well-designed and quickly constructed Ni(OH)2-Ni3Pt heterointerfaces reveal lower overpotentials for HER compared with most reported Pt-based and commercial Pt/C catalysts in nonacidic conditions. This study is expected to provide useful reference information for the development of facile and robust methods for the preparation of more efficient Pt-based electrocatalysts.

Recovery of nickel ions from wastewater by precipitation approach using silica xerogel

A facile route was developed to recover nickel ions from a synthetic wastewater. It involved the use of silica xerogel containing amine in the nickel sulphate solution resulting in the formation of a greenish precipitate. It was found that this precipitate was mostly amorphous Ni(OH)₂ spherical aggregate composed of nanosheets. The pH level of the solution was monitored, and it was maintained in the range of 10-10.5 due to the steady release of amine from the xerogel into the waste solution. The prepared silica xerogel would provide a stable environment for the chemical precipitation of metal ions in wastewater during the whole precipitation process. The silica xerogel was collected and reused for two more cycles of recovery. The nickel removal efficiencies (99.34˜99.65%) kept unchanged and higher than those reported earlier. The collected precipitate that contained nickel hydroxide with some residual silica could be utilized as glass colorant.

Molecular structure and interactions of water intercalated in nickel hydroxide

The structure and properties of α-Ni(OH)2 containing water and nitrate have been investigated computationally. The adsorption of water molecules on the Ni(OH)2 surface is also investigated to provide insight into the nature of the water-Ni(OH)2 interactions. The spectroscopic and dynamical behaviour of the intercalated species has been characterized and used to explain experimental findings reported for this material. The results presented here indicate that the water molecules interact non-covalently with Ni(OH)2, with a binding energy that is comparable in magnitude with that of the water dimer hydrogen bond. The presence of the intercalated species increases the distance between the Ni(OH)2 layers such that the interlayer interactions are negligible. The weakening of the interlayer interactions facilitates the horizontal displacement of the layers relative to one another, providing a possible origin for stacking faults observed in α-Ni(OH)2. Comparison of the vibrational frequencies calculated here with the experimental spectra confirms that α-Ni(OH)2 containing only water molecules can be synthesized. The structures of the water molecules intercalated in α-Ni(OH)2 were found to be analogous to those absorbed in γ-NiOOH, while the water-layer interactions are stronger in γ-NiOOH. The results presented here characterize the structure and interactions of water intercalated in nickel hydroxides and also provide insights into the effects of intercalated water on the properties of layered metal hydroxides.

Influence of PEG Stoichiometry on Structure-Tuned Formation of Self-Assembled Submicron Nickel Particles

Self-assembled submicron nickel particles were successfully synthesized via the one-step surfactant-assisted solvothermal method. The impact of surfactant and reducing agent stoichiometry is investigated in this manuscript. Different morphologies and structures of Ni particles, including flower-like nanoflakes, hydrangea-like structures, chain structures, sphere-like structures, and hollow structures were prepared through different processing conditions with two parameters such as temperature and time. Based on scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and vibrating sample magnetometry (VSM), the submicron nickel particles show good saturation magnetization and excellent thermal stabilities with a possible growth mechanism for the variety of the structure-tuned formation. Importantly, the microwave absorption properties of the submicron nickel particles were studied. The lowest reflection loss of Ni-P₉/T₂₀₀/H₁₅ with a thin layer thickness of 1.7 mm can reach -42.6 dB at 17.3 GHz.

A comprehensive investigation on adsorption of Ca (II), Cr (III) and Mg (II) ions by 3D porous nickel films

The present study reports the removal of Ca (II), Cr (III), Mg (II) ions from aqueous solution using 3D-porous nickel films (3DNFs) as a novel adsorbent material prepared by hydrogen bubble dynamic template (HBDT) method at room temperature. The structure morphology and the phase constitution of 3DNFs were characterized by FESEM, EDS and XRD. Adsorption process of Ca (II), Cr (III), Mg (II) ions was fast as the equilibrium was established within 30min, and the maximum adsorption at equilibrium was 44.1mg/g, 46.4mg/g and 32.7mg/g, respectively. The adsorption kinetics well fitted using a pseudo second-order kinetic model. The adsorption isotherm data of all the three metals fit well the Langmuir and Freundlich adsorption isotherm model. It was found out that kinetics of adsorption varies with initial concentration of metal ions. Thermodynamic parameters (i.e., the standard Gibbs free energies (ΔG), enthalpy change (ΔH), standard entropy change (ΔS)) were also evaluated. Thermodynamic analysis indicated that a high temperature is favored for the adsorption of metal ions by 3DNFs. These results suggest that 3DNFs have good potential application in effective adsorption of metal ions with satisfactory results.

Rapid synthesis of hollow Ni(OH)2 with low-crystallinity for the electrochemical detection of ascorbic acid with high sensitivity

Ni(OH)₂ performed good properties to ascorbic acid detection with the linear range of 10 μM to 0.20 mM, the detection limit of 3 μM (S/N = 3). The sensitivity is 1747.71 μA mM⁻¹ cm⁻², which is due to the hollow Ni(OH)₂ with low crystallinity.

Fast synthesis and electrochemical performance of hollow NiCo2O4 flowerlike microstructures

Hollow NiCo₂O₄ flowerlike microstructures with good electrochemical performance were successfully prepared through a fast microwave-assisted hydrothermal route and sequential pyrolysis.

The influence of aluminum chloride on biosynthetic schwertmannite and Cu(ii)/Cr(vi) adsorption

In this study, aluminium chloride modified schwertmannite was biosynthesized using Acidithiobacillus ferrooxidans. Heavy metals can be efficiently removed by the modified biosynthetic schwertmannite.

Simple hydrothermal synthesis and photocatalytic performance of coral-like BaTiO3 nanostructures

Coral-like BaTiO₃ nanostructures with good photocatalytic performances were successfully prepared through a simple hydrothermal route.