19192-71-3Relevant articles and documents
Size and doping effects on the improvement of the low-temperature magnetic properties of magnetically aligned cobalt ferrite nanoparticles
Knobel, Marcelo,Moscoso-Londo?o, Oscar,Muraca, Diego,Rivas-Rojas, Patricia C.,Socolovsky, Leandro M.,Tancredi, Pablo
, (2021/11/01)
The macroscopic magnetic behavior of nanoparticulated systems is the result of several contributions, ranging from the intrinsic structural properties of the nanoparticles to their spatial arrangement within the material. Unravelling and understanding these influences is an important task to produce nano-systems with improved properties for specific technological applications. In this work we study how the magnetic behavior of a set of magnetically hard nanoparticles can be improved by the modification of the sample arrangement (either randomly or magnetically oriented) and the nature of the enclosing matrices. At first, we employed a hot-injection, continuous growth strategy to synthesize non-stoichiometric cobalt ferrite (CoxFe3?xO4) nanoparticles. We prepared five batches of hydrophobic, oleate-coated samples, with mean diameters of 8 nm, 12 nm, 16 nm and variable Co-to-Fe proportions. The structural characterization confirms that the nanoparticles have a spinel-type monocrystalline structure and that the Co and Fe ions are homogenously distributed within the system. The magnetic properties of the nanoparticles were measured by DC magnetometry, and we found that the strategy used in this work to create a system of magnetically oriented nanoparticles can lead to a significant remanence and coercive field enhancement at low temperatures when compared with randomly oriented and fixed systems. The modification of the magnetic properties was detected in the five batches of samples, but the strength of the enhancement depends on both size and composition of the nanoparticles. Indeed, for the “hardest” samples the coercive field of the magnetically oriented systems reached values of around 30 kOe (3 T), which represents a 50% increase regarding the randomly oriented system and are among the highest reported to date for a set of Fe and Co oxide nanoparticles.
Ultrathin Amorphous Nickel Doped Cobalt Phosphates with Highly Ordered Mesoporous Structures as Efficient Electrocatalyst for Oxygen Evolution Reaction
Yang, Lan,Ren, Hao,Liang, Qinghua,Dinh, Khang Ngoc,Dangol, Raksha,Yan, Qingyu
, (2020/02/04)
Herein, the facile preparation of ultrathin (≈3.8 nm in thickness) 2D cobalt phosphate (CoPi) nanoflakes through an oil-phase method is reported. The obtained nanoflakes are composed of highly ordered mesoporous (≈3.74 nm in diameter) structure and exhibit an amorphous nature. Attractively, when doped with nickel, such 2D mesoporous Ni-doped CoPi nanoflakes display decent electrocatalytic performances in terms of intrinsic activity, and low kinetic barrier toward the oxygen evolution reaction (OER). Particularly, the optimized 10 at% Ni-doped CoPi nanoflakes (denoted as Ni10-CoPi) deliver a low overpotential at 10 mA cm?2 (320 mV), small Tafel slope (44.5 mV dec?1), and high stability for OER in 1.0 m KOH solution, which is comparable to the state-of-the-art RuO2 tested in the same condition (overpotential: 327 mV at 10 mA cm?2, Tafel slope: 73.7 mV dec?1). The robust framework coupled with good OER performance enables the 2D mesoporous Ni10-CoPi nanoflakes to be a promising material for energy conversion applications.
One-step solid phase synthesis of a highly efficient and robust cobalt pentlandite electrocatalyst for the oxygen evolution reaction
Al-Mamun, Mohammad,Wang, Yun,Liu, Porun,Zhong, Yu Lin,Yin, Huajie,Su, Xintai,Zhang, Haimin,Yang, Huagui,Wang, Dan,Tang, Zhiyong,Zhao, Huijun
, p. 18314 - 18321 (2016/12/09)
Cobalt pentlandite (Co9S8) has recently emerged as an alternative non-noble metal based electrocatalyst for the oxygen evolution reaction (OER). Co9S8 is known for its intrinsic structural and electronic properties favorable for electrocatalytic applications, but the synthesis of stoichiometrically optimal Co9S8 electrocatalysts remains challenging. Herein, a facile one-step solid phase calcination approach is presented in which Co9S8 nanoparticles (NPs) were concurrently synthesised on carbon nanosheets (CNSs). The reaction mechanism for this synthesis was systematically investigated using TG/DSC-MS analysis. Relative to other cobalt chalcogenide electrocatalysts, the as-prepared thermally stable nanocomposite (Co9S8/CNS) has better electrocatalytic performance for the OER in alkaline electrolytes, exhibiting a smaller overpotential of 294 mV at a current density of 10 mA cm2 with a Tafel slope of 50.7 mV dec1. Furthermore, a minimum overpotential of 267 mV with a Tafel slope of 48.2 mV dec1 could be achieved using highly conducting multi-walled carbon nanotubes (MWCNTs) as a conducting filler in the nanocomposites.
Rapid and large-scale synthesis of bare Co3O4 porous nanostructures from an oleate precursor as superior Li-ion anodes with long-cycle lives
Ge, Danhua,Wu, Junjie,Qu, Genlong,Deng, Yaoyao,Geng, Hongbo,Zheng, Junwei,Pan, Yue,Gu, Hongwei
, p. 13509 - 13513 (2016/09/04)
In this study, we describe a rapid and environmentally friendly synthesis of bare Co3O4 nanocrystals derived from Co(ii) oleate complexes by calcination treatment. When directly used as anode materials for lithium-ion batteries (LIBs), the as-prepared nanocrystals could deliver a high reversible capacity of 980 mA h g-1 after 250 cycles at a current density of 100 mA g-1 and excellent cycling performance, which may be beneficial to promote the further development of the next generation of lithium ion batteries. The synthetic route can offer great advantages for the flash preparation of other metal oxide nanocrystals for energy storage application.
Facet-dependent catalytic activity of MnO electrocatalysts for oxygen reduction and oxygen evolution reactions
Kuo, Chung-Hao,Mosa, Islam M.,Thanneeru, Srinivas,Sharma, Vinit,Zhang, Lichun,Biswas, Sourav,Aindow, Mark,Pamir Alpay,Rusling, James F.,Suib, Steven L.,He, Jie
supporting information, p. 5951 - 5954 (2015/03/30)
This Communication highlights the facet-dependent electrocatalytic activity of MnO nanocrystals for OERs/ORRs. The MnO(100) facets with higher adsorption energy of O species can largely promote the electrocatalytic activity.
Nanoparticle-sulphur "inverse vulcanisation" polymer composites
Bear, Joseph C.,Peveler, William J.,McNaughter, Paul D.,Parkin, Ivan P.,O'Brien, Paul,Dunnill, Charles W.
supporting information, p. 10467 - 10470 (2015/06/25)
Composites of sulphur polymers with nanoparticles such as PbS, with tunable optical properties are reported. A hydrothermal route incorporating pre-formed nanoparticles was used, and their physical and chemical properties evaluated by transmission and scanning electron microscopy, thermogravimetric and elemental analyses. These polymers are easily synthesised from an industrial waste material, elemental sulphur, can be cast into virtually any form and as such represent a new class of materials designed for a responsible energy future.
Synthesis of two-dimensional transition-metal phosphates with highly ordered mesoporous structures for lithium-ion battery applications
Yang, Dan,Lu, Ziyang,Rui, Xianhong,Huang, Xiao,Li, Hai,Zhang, Wenyu,Lam, Yeng Ming,Hng, Huey Hoon,Zhang, Hua,Yan, Qingyu,Zhu, Jixin
supporting information, p. 9352 - 9355,4 (2015/02/02)
Materials with ordered mesoporous structures have shown great potential in a wide range of applications. In particular, the combination of mesoporosity, low dimensionality, and well-defined morphology in nanostructures may exhibit even more attractive features. However, the synthesis of such structures is still challenging in polar solvents. Herein, we report the preparation of ultrathin two-dimensional (2D) nanoflakes of transition-metal phosphates, including FePO4, Mn3(PO4)2, and Co3(PO4)2, with highly ordered mesoporous structures in a nonpolar solvent. The as-obtained nanoflakes with thicknesses of about 3.7nm are constructed from a single layer of parallel-packed pore channels. These uniquely ordered mesoporous 2D nanostructures may originate from the 2D assembly of cylindrical micelles formed by the amphiphilic precursors in the nonpolar solvent. The 2D mesoporous FePO4 nanoflakes were used as the cathode for a lithium-ion battery, which exhibits excellent stability and high rate capabilities. Ultrathin two-dimensional (2D) nanoflakes of transition-metal phosphates, including FePO4 (see TEM image), Mn 3(PO4)2, and Co3(PO 4)2, with highly ordered mesoporous structures have been successfully synthesized in a nonpolar solvent. The use of the 2D mesoporous FePO4 nanoflake as a cathode in a lithium-ion battery resulted in excellent stability and high rate capabilities.
Insights into the thermal decomposition of Co(II) oleate for the shape-controlled synthesis of wurtzite-type CoO nanocrystals
Buck, Matthew R.,Biacchi, Adam J.,Schaak, Raymond E.
, p. 1492 - 1499 (2014/03/21)
Fatty acid salts of transition metals are known to undergo thermal decomposition in high-boiling organic solvents. Although it is a straightforward, promising approach for generating colloidal metal oxide nanocrystals in high yield, its widespread implementation is hindered by irreproducibility. Subtle structural variations and impurities are often introduced during preparation of the carboxylate precursors, which exhibit strong influence on thermal decomposition, and the resulting nucleation and growth of oxide nanocrystals. Here, we studied the colloidal synthesis of wurtzite-type CoO (wz-CoO) nanostructures via thermal decomposition of Co(II) oleate complex [Co(OL)]2. Using Fourier transform infrared spectroscopy, we discovered that the conventional method for preparing [Co(OL)]2 gives rise to an isolable impurity containing a free hydroxide moiety. Furthermore, [Co(OL)]2 did not thermally decompose within the expected temperature range when the impurity was removed. In contrast, pencil-shaped wz-CoO nanorods were synthesized when no measures were taken to remove the impurity, suggesting that the hydroxide functionality may facilitate the thermal decomposition. These insights enabled us to prepare size-and shape-controlled wz-CoO nanocrystals using purified [Co(OL)] 2 solutions, by incorporating additives that mimic the action of the hydroxide impurity. We also demonstrate a simplified pathway to wz-CoO nanocrystals that does not require chemical additives for thermolysis.
Studies on the Behaviour of Cobalt and Calcium Soaps. Part I. Solubility Studies in Non-aqueous Solvents
Varma, R. P.,Jain, P. K.
, p. 98 - 100 (2007/10/02)
Solubilities of laureates and oleates of calcium and cobalt have been measured in organic solvents at temperatures 35-60 deg and the same has been found to increase with the rise in temperature showing a marked change at Krafft point.The values of heat of solution, ΔHs and entropy of solution, ΔSsol have been calculated.These parameters suggest the presence of soap micelles in the solutions above Krafft point.
