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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.


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Journal ArticleDOI
TL;DR: In this article, the structure of alumina-supported cobalt catalysts promoted with platinum and their catalytic performance in Fischer-Tropsch synthesis were investigated under realistic reaction conditions.

226 citations

Journal ArticleDOI
TL;DR: In this paper, an arc discharge process modified in the geometry of the anode and the flow pattern of helium gas was used to produce carbon-coated iron, cobalt, and nickel particles.
Abstract: Carbon‐coated iron, cobalt, and nickel particles were produced by an arc discharge process modified in the geometry of the anode and the flow pattern of helium gas. Field emission scanning electron microscopy shows that the resulting material consists of only carbon‐coated metal particles without any nanotubes or other unwanted carbon formations present. The diameters of iron, cobalt, and nickel particles range predominantly from 32 to 81 nm, 22 to 64 nm, and 16 to 51 nm, respectively. X‐ray diffraction analysis confirmed that the as‐made particles are carbon‐coated elements rather than metal carbides. High resolution transmission electron microscopy reveals that the as‐made cobalt and nickel particles are covered by 1–2 graphitic layers, while iron particles are surrounded by amorphous carbon. When the samples were treated by annealing or immersion into nitric acid, particles completely coated by carbon resisted both postdeposition treatments. However, further graphitization of the carbon coating by eith...

225 citations

Journal ArticleDOI
TL;DR: A cobalt-containing metal-organic framework using adenine as a ligand was synthesized and pyrolyzed without any other precursors, forming a cobalt nanoparticle-embedded nitrogen-doped carbon/carbon nanotube framework (Co@N-CNTF) as discussed by the authors.
Abstract: Developing active and stable electrocatalysts of earth-abundant elements towards the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) still remains a crucial challenge. Herein, a cobalt-containing metal-organic framework using adenine as a ligand was synthesized and pyrolyzed without any other precursors, forming a cobalt nanoparticle-embedded nitrogen-doped carbon/carbon nanotube framework (Co@N-CNTF). Due to the abundant active sites of homogeneously distributed cobalt nanoparticles within nitrogen-doped graphitic layers, the resultant Co@N-CNTF catalysts exhibit an efficient and stable electrocatalytic performance as a tri-functional catalyst towards the ORR, OER and HER, including a high half-wave potential of 0.81 V vs. RHE for the ORR, and a low overpotential at 10 mA cm -2 for the OER (0.35 V) and HER (0.22 V). As a proof-of-concept, the Co@N-CNTF as an OER/HER bifunctional catalyst for full water splitting affords an alkaline electrolyzer with 10 mA cm -2 under a stable voltage of 1.71 V. Moreover, an integrated unit of a water-splitting electrolyzer using the Co@N-CNTF catalysts, which is powered with a rechargeable Zn-air battery using the Co@N-CNTF as an ORR/OER bifunctional catalyst on air electrodes, can operate under ambient conditions with high cycling stability, demonstrating the viability and efficiency of the self-powered water-splitting system.

225 citations

Journal ArticleDOI
TL;DR: In this article, the authors examined the kinetics of desorption of Cd and Co from two Fe oxides, goethite and ferrihydrite, and from two Mn oxides (hausmannite and cryptomelane).
Abstract: Oxides of Fe and Mn in soils are capable of sorbing large amounts of trace metal ions and can therefore be important in controlling trace metal concentrations in soil solution, and hence trace metal bioavailability in soils. There is, however, relatively little information on the rates of desorption of trace metals from oxide materials or on the factors affecting desorption rates. The objective of this study was to examine the kinetics of desorption of Cd and Co from two Fe oxides, goethite and ferrihydrite, and from two Mn oxides, hausmannite and cryptomelane. The concentrations of Cd and Co specifically sorbed by the oxides at pH 6.0 were greater for the Mn oxides than for the Fe oxides. The metals were also much less readily desorbed from the Mn than the Fe oxides and, in general, Cd was more readily desorbed than Co from all four oxides. Increasing the initial sorption period from 1 to 15 wk substantially decreased the proportion of sorbed Cd or Co subsequently desorbed from goethite, with a similar but much smaller effect also observed with the Mn oxides. Desorption kinetics for both Cd and Co were found to be described well by assuming either the occurrence of two simultaneous first-order desorption reactions, or by a continuous distribution of reaction sites, distributed lognormally with respect to desorption first-order rate constant. With increasing initial sorption period, the parameters obtained from fitting either type of kinetic equation to the experimental data could be interpreted as indicating a movement of metal ions to sites with slower desorption reactions.

225 citations

Journal ArticleDOI
01 Mar 2017-Small
TL;DR: Highly optimized nickel cobalt mixed oxide has been derived from zeolite imidazole frameworks, which has given an extremely high and unprecedented specific capacitance and shows a significant improvement in the cyclic stability with 81% capacitance retention after 5000 cycles.
Abstract: Highly optimized nickel cobalt mixed oxide has been derived from zeolite imidazole frameworks. While the pure cobalt oxide gives only 178.7 F g-1 as the specific capacitance at a current density of 1 A g-1 , the optimized Ni:Co 1:1 has given an extremely high and unprecedented specific capacitance of 1931 F g-1 at a current density of 1 A g-1 , with a capacitance retention of 69.5% after 5000 cycles in a three electrode test. This optimized Ni:Co 1:1 mixed oxide is further used to make a composite of nickel cobalt mixed oxide/graphene 3D hydrogel for enhancing the electrochemical performance by virtue of a continuous and porous graphene conductive network. The electrode made from GNi:Co 1:1 successfully achieves an even higher specific capacitance of 2870.8 F g-1 at 1 A g-1 and also shows a significant improvement in the cyclic stability with 81% capacitance retention after 5000 cycles. An asymmetric supercapacitor is also assembled using a pure graphene 3D hydrogel as the negative electrode and the GNi:Co 1:1 as the positive electrode. With a potential window of 1.5 V and binder free electrodes, the capacitor gives a high specific energy density of 50.2 Wh kg-1 at a high power density of 750 W kg-1 .

225 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20232,622
20225,202
20212,220
20202,950
20193,215
20183,007