Cobalt Disulfide Research Articles

Cobalt disulfide nanowires as an effective fluorescent sensing platform for DNA detection.

In this communication, for the first time, the facile production of cobalt disulfide nanowires (CoS2 NWs) is achieved in solution using a two-step hydrothermal method and the formation mechanism of CoS2 NWs is based on the anion-exchange reaction involving the pseudo Kirkendall effect. As a proof-of-concept application, CoS2 NWs are applied as an effective fluorescent sensing platform for the detection of nucleic acid and this nanosensor exhibits extraordinarily high sensitivity with a detection limit as low as 10 pM and good selectivity. Most importantly, the successful use of this sensing platform in the fetal bovine serum system is also demonstrated.

Selective synthesis of pure cobalt disulfide on reduced graphene oxide sheets and its high electrocatalytic activity for hydrogen evolution reaction

Selective synthesis of pure cobalt disulfide on reduced graphene oxide sheets and its high electrocatalytic activity for hydrogen evolution reaction

Nickel promoted cobalt disulfide nanowire array supported on carbon cloth: An efficient and stable bifunctional electrocatalyst for full water splitting

Development of efficient noble metal-free bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an ongoing challenge. Herein, we report the development of nickel promoted cobalt disulfide nanowire array supported on carbon cloth (Ni2.3%-CoS2/CC) as an efficient bifunctional electrocatalyst for water splitting with superior activity and good durability in basic media. This Ni2.3%-CoS2/CC electrode delivers 100mAcm−2 at overpotential of 231mV for HER and 100mAcm−2 at overpotential of 370mV for OER. The water electrolyzer based on Ni2.3%–CoS2/CC only requires a cell voltage of 1.66V to afford 10mAcm−2, implying the great potential for water splitting applications.

Transport and magnetic properties of cobalt disulfide prepared by solid state hybrid microwave heating and hot pressing

In this study, single phase cobalt disulfide [Formula: see text] was synthesized by temperature-controlled solid state hybrid microwave heating. The structure, composition and morphology of the obtained samples were studied using X-ray diffraction (XRD), scanning electron spectroscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and high resolution transmission electron microscopy (HRTEM), respectively. The loose [Formula: see text] polycrystalline precursor was then hot pressed to dense bulk sample. The subsequent transport and magnetic properties measurements reveal the ferromagnetic Curie temperature at the magnetic transition near 128 K. These results suggest that the magnetic transition in [Formula: see text] is susceptible to the preparation conditions and the microstructure of the samples.

Shape-controlled octahedral cobalt disulfide nanoparticles supported on nitrogen and sulfur-doped graphene/carbon nanotube composites for oxygen reduction in acidic electrolyte

Shape controlled cobalt disulfide octahedron nanoparticles are grown on nitrogen/sulfur-doped carbon nanotube-graphene composites as active non-precious oxygen reduction catalysts.

An integrated cobalt disulfide (CoS2) co-catalyst passivation layer on silicon microwires for photoelectrochemical hydrogen evolution

Cobalt disulfide layer modified-Si microwires were used as photocathode materials for solar hydrogen evolution, showing a stable photocurrent of −3 mA cm−2 at 0 V for 9 h.

The facile preparation of a cobalt disulfide-reduced graphene oxide composite film as an efficient counter electrode for dye-sensitized solar cells.

Cobalt disulfide (CoS2)-reduced graphene oxide (RGO) composite (CSG) films, which are prepared by combining the layer by layer assembly method and thermal treatment process, are used as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The DSSC with CSG CE exhibits comparable efficiency to the cell with the Pt CE.

Multi-objective optimization of reaction parameters and kinetic studies of cobalt disulfide nanoparticles

In this study, cobalt disulfide (CoS2) nanoparticles have been successfully synthesized through a simple and facile solvothermal method. The experiments were carried out based on the thermodynamic calculations using FactSage software. The black nano-sized CoS2 powder has been produced in an autoclave reactor. The reaction parameters, such as the ratio of primary salts, effect of solvents, temperature and surfactant were optimized to obtain fine and uniform nanoparticles. The band gap energy of the samples was measured with butler relations. The results proved the production of highly pure CoS2 nanoparticles with a semi-spherical morphology.

A free template strategy for the synthesis of CoS2-reduced graphene oxide nanocomposite with enhanced electrode performance for supercapacitors

A nanocomposite of cobalt disulfide (CoS2) nanoparticles and chemically reduced graphene oxide (RGO) sheets was prepared through a facile solvothermal method without any template. The structural and morphological properties of CoS2–RGO nanocomposite were characterized through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectra and thermo-gravimetric analysis. The electrochemical behavior of CoS2–RGO nanocomposite has been investigated using cyclic voltammograms, galvanostatic charge/discharge and electrochemical impedance spectroscopy in 6M KOH electrolyte. A maximum specific capacitance of 331Fg−1 was obtained at a current rate of 0.5Ag−1 with a wide working potential window from −0.3 to 0.65V.

High-performance electrocatalysis using metallic cobalt pyrite (CoS₂) micro- and nanostructures.

The development of efficient and robust earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) is an ongoing challenge. We report metallic cobalt pyrite (cobalt disulfide, CoS2) as one such high-activity candidate material and demonstrate that its specific morphology--film, microwire, or nanowire, made available through controlled synthesis--plays a crucial role in determining its overall catalytic efficacy. The increase in effective electrode surface area that accompanies CoS2 micro- and nanostructuring substantially boosts its HER catalytic performance, with CoS2 nanowire electrodes achieving geometric current densities of -10 mA cm(-2) at overpotentials as low as -145 mV vs the reversible hydrogen electrode. Moreover, micro- and nanostructuring of the CoS2 material has the synergistic effect of increasing its operational stability, cyclability, and maximum achievable rate of hydrogen generation by promoting the release of evolved gas bubbles from the electrode surface. The benefits of catalyst micro- and nanostructuring are further demonstrated by the increased electrocatalytic activity of CoS2 nanowire electrodes over planar film electrodes toward polysulfide and triiodide reduction, which suggests a straightforward way to improve the performance of quantum dot- and dye-sensitized solar cells, respectively. Extension of this micro- and nanostructuring strategy to other earth-abundant materials could similarly enable inexpensive electrocatalysts that lack the high intrinsic activity of the noble metals.

Taguchi based fuzzy logic optimization of multiple quality characteristics of cobalt disulfide nanostructures

Cobalt sulfide nanostructures, with a formula of CoxSy, have recently received considerable attention due to their unique catalytic, electric, magnetic, optical, and mechanical properties. In this study, cobalt disulfide (CoS2) nanoparticles have been synthesized by the solvothermal method using cobalt chloride and sodium thiosulfate as the precursors. The Taguchi method has been implemented to investigate and optimize the affecting parameters involved in minimizing the band-gap energy. Then, the predictions used to model the anticipated results with fuzzy logic. It has been found that the reaction temperature and the precursor ratio are the most effective parameters when attempting to minimize the band-gap energy.

Synthesis and Properties of Cobalt Sulfide Phases: CoS2 and Co9S8

AbstractSingle phase cobalt disulfide (CoS2) nanoparticles were prepared by thermal decomposition of cobalt‐thiourea complex at a low temperature (400 °C). CoS2 nanoparticles exhibit ferromagnetic ordering at 122 K below which the temperature dependent resistivity of cold pressed nanoparticles deviates from metallic behavior and shows a broad maximum. Just below TC, it also exhibits a large magnetoresistance effect (6.5 %). A mixture of CoS and Co9S8 phases were obtained between the temperature interval 400 °C < T < 1000 °C. At 1000 °C, a pure bulk Co9S8 phase was obtained. It exhibits magnetic hysteresis typical of a ferromagnet at room temperature and a peak in magnetization at low temperature with a strong relaxation indicating possible spin glass state.

Earth-Abundant Cobalt Pyrite (CoS2) Thin Film on Glass as a Robust, High-Performance Counter Electrode for Quantum Dot-Sensitized Solar Cells.

We report a cobalt pyrite (cobalt disulfide, CoS2) thin film on glass as a robust, high-performance, low-cost, earth-abundant counter electrode for liquid-junction quantum dot-sensitized solar cells (QDSSCs) that employ the aqueous sulfide/polysulfide (S(2-)/Sn(2-)) redox electrolyte as the hole-transporting medium. The metallic CoS2 thin film electrode is prepared via thermal sulfidation of a cobalt film deposited on glass and has been characterized by powder X-ray diffraction and electron microscopy. Using the CoS2 counter electrode, CdS/CdSe-sensitized QDSSCs display improved short-circuit photocurrent density and fill factor, achieving solar light-to-electricity conversion efficiencies as high as 4.16%, with an average efficiency improvement of 54 (±14)% over equivalent devices assembled with a traditional platinum counter electrode. Electrochemical measurements verify that CoS2 shows high electrocatalytic activity toward polysulfide reduction, rationalizing the improved QDSSC performance. CoS2 is also less susceptible to poisoning by the sulfide/polysulfide electrolyte, a problem that plagues platinum electrodes in this application; furthermore, CoS2 exhibits excellent stability in sulfide/polysulfide electrolyte, resulting in highly reproducible performance.

Attaching high charge density metal ions to surfaces and biomolecules. Reaction chemistry of hypodentate cobalt diamine complexes

Hypodentate diamine cobalt(III) pentammine complexes [Co(NH3)5(NH2(CH2)(n)NH3)](ClO4)4 (8: a: n = 3; b: n = 4; c: n = 6; d: n = 8) have been synthesized via the reaction of [Co(NH3)5(OTf)](OTf)2 (TfOH = CF3SO3H) with the corresponding diamines. The analogous t-boc protected diamine complexes [Co(NH3)5(NH2(CH2)(n)NHt-boc)](ClO4)3 (7a-d) were prepared in 4-26% yield. Low yields for the formation of 7a-d are due to competing side reactions which also gave [Co(NH3)6](3+). Complexes 7a-d were deprotected using trifluoroacetic acid to give the corresponding hypodentate diamine complexes [Co(NH3)5(NH2(CH2)(n)NH3)](CF3CO2)0.5(ClO4)3.5 (9a-d). HBTU coupling of 8c with N-(t-boc)-L-phenylalanine gave an amino acid functionalized cobalt pentammine complex [Co(NH3)5(NH2(CH2)6NHt-boc)-L-phenylalanine)](ClO4)3 (10). All new complexes were characterized using UV-vis and (1)H NMR spectroscopy, and elemental analysis. Grafting of 8c onto 2.4 mm poly(ethylene-co-acrylic acid) (PEAA) beads was achieved via amide coupling. Complex 8c was coupled to thioctic acid via amide coupling and the resulting cobalt disulfide complex [Co(NH3)5(N-(6-aminohexyl)-5-(1,2-dithiolan-3-yl)pentanamide)](ClO4)3 (11) was attached to 10 nm Au nanoparticles. The amount of cobalt loading onto PEAA beads and Au nanoparticles was determined using ICP-MS and EDX.

Synthesis of well dispersed cobalt disulfide and their photoluminescence and magnetic properties

We used a facile solvothermal method to synthesize well dispersed pyrite cobalt disulfide nanoparticles by using sulfur powder and ethylenediamine as sulfur source and solvent, respectively. The chemical composition of the nanoparticles is determined to be CoS1.931. These nanoparticles are of spherical and quasi-spherical shapes, and the diameters are in the range from 20 to 60nm. Photoluminescence spectra show two emission bands centered at 411 and 532nm, respectively. Magnetic measurement indicates a broad homogeneous ferromagnetic–paramagnetic transition with Tcca. 140K. It is found that intrinsic point defects including VS, Coi, CoS, Si may be the main reason for the unusual emission bands and increased Tc.

A Study of the CoS2 Cathode for Thermal Batteries

A detailed evaluation of the Li(Si)/LiCl-LiBr-LiF/CoS2 electrochemical system and Li(Si)/LiCl-LiBr-LiF/FeS2 one is undertaken. Test results show that the internal resistance of batteries based on cobalt disulfide (CoS2) cathode is 24% less than that based on iron disulfide (FeS2) cathode, that the peak voltage in parallel of 17 cells based on CoS2 cathode is 32.3V, but that based on CoS2 cathode is 33.5V. The performance comparison of thermal batteries based on CoS2 cathode was evaluated at 25°, -47°, and +62°, respectively. Test results show that the discharge curves at different temperature almost lap over.

Evidence for H 2S gas as an intermediate species in the reaction mechanism of trapping hydrogen by cobalt disulfide

Cobalt sulfide prepared by aqueous precipitation using Na 2S and a Co(II) salt is known to trap hydrogen at room temperature and low pressure. The importance of oxidation of the primary CoS precipitate with atmospheric oxygen with respect to its efficiency as a hydrogen absorber is demonstrated. This stage of oxidation produces a mixture of two solid phases: a partially crystallized cobalt hydroxide Co(OH) 2 and an amorphous cobalt sulfide CoS 2 with a Co(OH) 2/CoS 2 molar ratio of 1 as predicted by thermodynamics. This biphasic product is probably the basic cobalt sulfide CoSOH considered in older and even more recent work. This product traps molecular hydrogen with a H 2/Co molar ratio of 0.5 whereas unoxidized CoS precipitate traps almost no hydrogen (H 2/Co = 0.025). Moderate acidic treatment of the absorber at room temperature leads to the selective dissolution of Co(OH) 2. The remaining cobalt sulfide has CoS 2 stoichiometry and reacts with hydrogen to form H 2S gas and CoS. We showed that H 2S released is reactive toward bases: CoS or Na 2S were formed when H 2S reacted with Co(OH) 2 or NaOH, respectively. This proves that the hydrogen trapping reaction mechanism implies H 2S as an intermediate species.

Synthesis of cobalt sulfide nanostructures by a facile solvothermal growth process

We reported a facile and efficient solvothermal route to produce cobalt sulfide (CoS) nanoflakes and cobalt disulfide (CoS2) nanoparticles in pure diethylenetriamine solvent. The CoS nanoflakes and CoS2 nanopaticles were obtained by using thiourea and sulfur powders as precursors, respectively. The CoS nanoflakes are of regular hexagonal shapes, and are single crystal with hexagonal phase. The obtained CoS2 nanoparticles are of single-crystalline cubic structures and the average size is about 5 nm. Moreover, it is found that the quantity of thiourea influences the corresponding morphologies of the CoS nanostructures, but has no effects on their phase structures. The formation mechanisms of the nanostructures were investigated and presented some new features that may be applied in synthesis of other transition metal sulfide nanostructures.

Synthesis and electrochemical performanceof cobalt disulfide

The anode material cobalt disulfide for lithium-ion batteries was synthesized using the hydrothermal method at a lower temperature. The microstructure and surface morphology of the powders were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical tests showed that this sample had superior electrochemical properties. The first discharge capacity is up to 1313.9 mAh/g in the voltage range of 3.00–0.02 V at a current density of 50 mA/g. Adjusting the voltage range to 3.00–0.50 V, the first discharge capacity decreases, but the 20th discharge capacity is 435.5 mAh/g, which is better than what has been reported in the literature.

Structure and Properties of Cobalt Disulfide Nanowire Arrays Fabricated by Electrodeposition

Highly ordered arrays of parallel cobalt disulfide nanowires with a diameter of about 40 nm and a length up to several tens of micrometers were synthesized by two electrical fields in an anodized aluminum oxide film. The cobalt disulfide nanowires have a cubic pyrite structure. In the study of electrochemical properties, it is found that the reaction of cobalt disulfide is an intercalation reaction in the range of 1.6-3.0 V, while a redox reaction in the range of 0.02-1.6 V is probable. The CoS 2 nanowires are ferromagnetic and the easy magnetization direction is along the nanowire axes.