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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: The N2 complexes of iron that are described are the first thoroughly characterized examples to exhibit a 4-coordinate geometry.
Abstract: The chemistry of low-valent iron and cobalt has been slow to develop, due largely in part to a lack of ligand scaffolds that can stabilize these species. Using the anionic tris(phosphino)borate ligand, [PhB(CH_2PiPr_2)_3]-, we have stabilized reactive complexes of the type [P_3M-L] where L can be varied from weakly-donating π-acidic ligands (e.g. N_2), to strongly π-basic ligands where multiple bonding occurs between the metal and L (e.g. NR ^2-). In addition to stabilizing a broad range of ligand types in a variety of oxidation states, the [P_3M] template has been shown to mediate the coordination and activation of dinitrogen on both iron and cobalt. The reaction chemistry of the [P_3M-L] scaffolds will be presented in addition to synthetic strategies targeting high-valent species (M^(IV), L=N ^3-).

263 citations

Journal ArticleDOI
TL;DR: Density functional theory calculation results indicate that the desorption of OH* from cobalt sites is the rate-limiting step for both CoP and Co2 P in ORR and that the high content of phosphide can lower the reaction barrier.
Abstract: Highly efficient and stable electrocatalysts, particularly those that are capable of multifunctionality in the same electrolyte, are in high demand for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this work, highly monodisperse CoP and Co2 P nanocrystals (NCs) are synthesized using a robust solution-phase method. The highly exposed (211) crystal plane and abundant surface phosphide atoms make the CoP NCs efficient catalysts toward ORR and HER, while metal-rich Co2 P NCs show higher OER performance owing to easier formation of plentiful Co2 P@COOH heterojunctions. Density functional theory calculation results indicate that the desorption of OH* from cobalt sites is the rate-limiting step for both CoP and Co2 P in ORR and that the high content of phosphide can lower the reaction barrier. A water electrolyzer constructed with a CoP NC cathode and a Co2 P NC anode can achieve a current density of 10 mA cm-2 at 1.56 V, comparable even to the noble metal-based Pt/C and RuO2 /C pair. Furthermore, the CoP NCs are employed as an air cathode in a primary zinc-air battery, exhibiting a high power density of 62 mW cm-2 and good stability.

263 citations

Journal ArticleDOI
TL;DR: A family of pincer-ligated cobalt complexes has been synthesized and are active for the catalytic C-H borylation of heterocycles and arenes and a catalytic cycle that relies on a cobalt(I)-(III) redox couple is proposed.
Abstract: A family of pincer-ligated cobalt complexes has been synthesized and are active for the catalytic C−H borylation of heterocycles and arenes. The cobalt catalysts operate with high activity and under mild conditions and do not require excess borane reagents. Up to 5000 turnovers for methyl furan-2-carboxylate have been observed at ambient temperature with 0.02 mol % catalyst loadings. A catalytic cycle that relies on a cobalt(I)–(III) redox couple is proposed.

263 citations

Journal ArticleDOI
TL;DR: In this paper, a new method combining the precipitation of the metal precursor (cobalt nitrate) by oxalic acid with the hydrolysis and condensation of the silicium precursor (tetraethoxysilane) was proposed.
Abstract: Silica supported cobalt catalysts have been prepared by a new method combining the precipitation of the metal precursor (cobalt nitrate) by oxalic acid with the hydrolysis and condensation of the silicium precursor (tetraethoxysilane). Depending on the pH during preparation, the textural properties (BET specific surface area, porosity) of the Co/SiO 2 catalysts can be modified. In an acid medium (pathway A), the resulting silica is constituted by a polymeric net with few branchings, the catalysts are microporous. In basic medium (pathway B) silica is composed of more branched polymers leading to mesoporous catalytic systems. After calcination, the only crystallized phase detected by XRD is the Co 3 O 4 spinel. At 773 K, the surface degrees of reduction of the catalysts at cobalt isocontent (25 wt.% Co) as determined by XPS is of 81% and 69% for systems prepared by pathways A and B, respectively. The presence of small unreduced Co II suggests the existence of non-crystallized cobalt silicate formed during the reduction by reaction of CoO with silica. The activity for the CO + H 2 reaction for the 25 wt.% catalysts prepared by pathway A increased with the specific surface area which can be controlled by the preparation parameters. The reduction degree has a direct influence on the selectivity for the Co/SiO 2 catalysts. The presence of a part of unreduced cobalt (in interaction with the support) results in a better selectivity to the C 5 –C 13 fraction (gasoline), whereas a higher reduction degree of cobalt favors the production of higher molecular weight hydrocarbons (waxes) (C 22 + selectivity > 40%).

262 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