Topic
Nickel
About: Nickel is a research topic. Over the lifetime, 79308 publications have been published within this topic receiving 1210058 citations. The topic is also known as: Ni & element 28.
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TL;DR: The findings indicate that the increase in catalytic activity of films is accompanied by changes in oxidation state and structure that are reminiscent of those observed for conversion of β-NiOOH to γ-NiooH and consequently challenge the long-held notion that the β- NiOOH phase is a more efficient oxygen-evolving catalyst.
Abstract: An oxygen evolution catalyst that forms as a thin film from Ni(aq)2+ solutions containing borate electrolyte (Ni–Bi) has been studied by in situ X-ray absorption spectroscopy. A dramatic increase in catalytic rate, induced by anodic activation of the electrodeposited films, is accompanied by structure and oxidation state changes. Coulometric measurements correlated with X-ray absorption near-edge structure spectra of the active catalyst show that the nickel centers in activated films possess an average oxidation state of +3.6, indicating that a substantial proportion of nickel centers exist in a formal oxidation state of Ni(IV). In contrast, nickel centers in nonactivated films exist predominantly as Ni(III). Extended X-ray absorption fine structure reveals that activated catalyst films comprise bis-oxo/hydroxo-bridged nickel centers organized into sheets of edge-sharing NiO6 octahedra. Diminished long-range ordering in catalyst films is due to their ostensibly amorphous nature. Nonactivated films display...
550 citations
TL;DR: Electrodeposited Ni(OH)(2) on nickel foam with porous and 3D nanostructures has ultrahigh capacitance in the potential range -0.05-0.45 V, and a maximum specific capacitance as high as 3152 F g (-1) can be achieved in 3% KOH solution at a charge/discharge current density of 4 A g(-1).
540 citations
531 citations
TL;DR: In this paper, NiO/Ni composite films have been found to perform as superior electrodes in electrochemical capacitor applications, which can provide a specific capacitance of 50 to 64 F/g.
Abstract: Nano-sized NiO/Ni composite films have been found to perform as superior electrodes in electrochemical capacitor applications. These films can provide a specific capacitance of 50 to 64 F/g. The specific energy and specific power of these films were 25 to 40 kJ/kg and 4 to 17 kW/kg, respectively. These specific quantities are dependent on the microstructure of the films. Superior performance can be obtained from samples having rough surfaces and consisting of larger secondary particles (ca. 100 to 120 nm in diam).
530 citations
TL;DR: In this paper, surface and subsurface horizon samples of two soils were equilibrated with varying amounts of Ca(OH)/sub 2/ prior to metal addition, and the amount of all four metals retained was dependent upon pH of the soil sample.
Abstract: Lead, copper, nickel, and zinc adsorption by and desorption from pH-adjusted soils has been studied. Surface and subsurface horizon samples of two soils were equilibrated with varying amounts of Ca(OH)/sub 2/ prior to metal addition. The amount of all four metals retained was dependent upon pH of the soil sample, with retention dramatically increasing above pH 7.0 to 7.5. With the exception of Ni, at least 70 to 75% of the retained metal was extractable in 0.01N HCl. Nickel was somewhat less extractable, with that sorbed by the highest pH soils being the least extractable. Based on subsequent extractibility, the soils used appeared to have specific adsorption sites for Pb, Ni, and Cu but little or none for Zn. These studies cast some doubt on the concept of pH management for immobilizing heavy metals placed on the land in that sorbed metals were substantially extractable by 0.01M HCl, which has been used to estimate plant availability of soil ions.
522 citations