Cobalt

About: Cobalt is a research topic. Over the lifetime, 69899 publications have been published within this topic receiving 1242058 citations. The topic is also known as: Co & Element 27.

Hydrogen Generation from the Hydrolysis of Ammonia-borane and Sodium Borohydride Using Water-soluble Polymer-stabilized Cobalt(0) Nanoclusters Catalyst

Abstract: Polymer-stabilized cobalt(0) nanoclusters were prepared from the reduction of cobalt(II) chloride in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) stabilizer in methanol solution. PVP-stabilized cobalt(0) nanoclusters were found to be stable in solution and could be isolated as solid material and characterized by TEM, XPS, FT-IR, and UV−visible electronic absorption spectroscopy. PVP-stabilized cobalt(0) nanoclusters were employed as catalyst in the hydrolysis of sodium borohydride and ammonia-borane, which have been considered as solid-state hydrogen storage materials for portable fuel cell applications. PVP-stabilized cobalt(0) nanoclusters were found to be highly active catalyst in both hydrolysis reactions, even at room temperature. Kinetic studies show that the catalytic hydrolyses of sodium borohydride and ammonia-borane are both first order with respect to catalyst and substrate concentration in aqueous medium. The effect of the NaOH concentration on the catalytic activity of the PVP-stabilized...

Analysis of the Growth Mechanism of Coprecipitated Spherical and Dense Nickel, Manganese, and Cobalt-Containing Hydroxides in the Presence of Aqueous Ammonia

Abstract: Spherical and dense metal hydroxides were synthesized with a coprecipitation reaction in the presence of aqueous ammonia. The growth of the particles was studied by tracking the tap density and morphology with reaction time. The dependence of pH on the tap density and morphology of the particles synthesized in the coprecipitation reaction was determined for Ni(OH)2, Ni1/2Mn1/2(OH)2, and Ni1/3Mn1/3Co1/3(OH)2 The pH range at which particle growth occurred varied for the different metal hydroxides. Solving the chemical equilibria present in the coprecipitation reaction revealed that the pH range at which spherical particle growth occurred was due to the presence of metal coordinated with ammonia. On the basis of the experiments and analysis presented here, the metal hydroxide particle growth occurs by a dissolution−recrystallization type mechanism during synthesis.

Identification of rcnA (yohM), a Nickel and Cobalt Resistance Gene in Escherichia coli

Abstract: We report here on the isolation and primary characterization of the yohM gene of Escherichia coli. We show that yohM encodes a membrane-bound polypeptide conferring increased nickel and cobalt resistance in E. coli. yohM was specifically induced by nickel or cobalt but not by cadmium, zinc, or copper. Mutation of yohM increased the accumulation of nickel inside the cell, whereas cells harboring yohM in multicopy displayed reduced intracellular nickel content. Our data support the hypothesis that YohM is the first described efflux system for nickel and cobalt in E. coli. We propose rcnA (resistance to cobalt and nickel) as the new denomination of yohM.

Bioinspired Cobalt-Citrate Metal-Organic Framework as an Efficient Electrocatalyst for Water Oxidation.

Abstract: Efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts are closely associated with many important energy conversion technologies. Herein, we first report an oxygen-evolving cobalt–citrate metal–organic framework (MOF, UTSA-16) for highly efficient electrocatalytic water oxidation. Benefiting from synergistic cooperation of intrinsic open porous structure, in situ formed high valent cobalt species, and existing Co4O4 cubane, the UTSA-16 exhibits excellent activity toward OER catalysis in alkaline medium. The UTSA-16 needs only 408 mV to offer a current density of 10 mA cm–2 for OER catalysis, which is superior to that of most MOF-based electrocatalysts and the standard Co3O4 counterpart. The present finding provides a better understanding of electroactive MOFs for water oxidation.