Papers by Keyword: Co₃O₄

Abstract: The metal-air batteries, especially the Zinc-air batteries, are great solutions to the growing energy crisis with excellent rechargeable capacity. ORR is the key electro-chemical reaction in Zinc-air batteries, and the development of the ORR efficiency is being studied extensively. The doping of transition metal in Co₃O₄, with the basement of N-doped graphene have been confirmed to have catalytic activity which can be comparable to Pt/C. Herein, the Fe-doped Co₃O₄ supported by N-doped graphene is constructed as the catalyst of ORR, and that without Fe doping is also constructed as comparison. Through first-principle calculation, it shows that the adsorption energies to O₂ on the same site of each surface and on different sites on Fe-doped one. The partial density of state of the O₂ adsorption system shows the effects of electron transfer and orbital hybridization on catalysis, which provide evidence to the catalytic mechanism with Fe doping. The energy changes of each step in ORR on catalyst with Fe doping and without Fe doping show the shortcomings of the simulation, including the spin of Fe atoms. Thus the study confirms that the adding of Fe contributes to the catalystic capability compared to the pure Co₃O₄.

Abstract: Cobalt oxide thin film (Co₃O₄) has been prepared from cobalt chloride with distilled water on conducting glass substrates Fluorine doped Tin Oxide (FTO) at (400^ºC) by depositing chemical spray pyrolysis, with thickness (200 nm). The structural properties are studied by XRD. Also, optical properties and electrical properties of Co₃O₄ thin film are studied by UV spectroscopy and Cyclic voltammetry (CV) respectively. The effects of gamma irradiation on optical properties are also examined. XRD results showed that the film was polycrystalline with cubic structure having preferred orientation (111). The as-prepared Co₃O₄ film exhibits a noticeable EC behaviour with reversible colour which changes from dark grey to pale yellow with bleaching time (55 s) and colouring time (40 s). After irradiation, the optical properties showed that as the transmittance decrease leads to decrease the direct optical band gap from (3.68eV) to (3.55eV)

Abstract: We report on the porous Co₃O₄ nanorods synthesized by hydrothermal reaction and applied as an anode material for reversible lithium storage. The Co₃O₄ with porous nanorods structure increases the contact surface, shortens the diffusion path of ion/electron, and improves its structure stability and collaborative electronic transmission. Due to the nanoparticle subunits, the electrodes exhibit high electrochemical performance. Impressively, a high reversible discharge specific capacity of 1105 mAh g^-1 is obtained at 200 mA g^-1 after 50 cycles. This indicates the excellent potential of porous Co₃O₄ nanorods as an anode material for lithium ion batteries. Thus, the porous Co₃O₄ nanorods might open an insight for transition-metal oxides as energy storage materials.

Abstract: Co₃O₄ nanoflakes/N-doped graphene (NG) was synthesized through a facile two-step synthesis route. The phase composition and morphology of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS). It has been found that introduction of NG has effects on the morphology of Co₃O₄ and leads to a well distribution of Co₃O₄ nanoflakes. The electrochemical properties of as-synthesized materials were measured by cyclic voltammetry (CV), galvanostatic charge/discharge tests and electrochemical impedance spectroscopy (EIS). The composite presents an enhanced supercapacitor performance than the pristine Co₃O₄ nanoflakes, mainly due to the strong synergistic effect of the NG and Co₃O₄.

Abstract: Nonstoichiometry and chemical diffusion in Co₃O₄ oxide have been studied as a function of temperature (973-1173 K) and oxygen pressure (30-10⁵ Pa), using thermogravimetric techniques. It has been found that at very low oxygen pressures, close to the dissociation pressure of the oxide, interstitial cations and quasi-free electrons are the predominant point defects, while at high pressures cation vacancies and electron holes predominate. This behaviour is reflected in complex dependence of the deviation from stoichiometry, y, in the Co_3±yO₄ oxide on oxygen pressure. At low pressures, namely, deviation from stoichiometry decreases with increasing oxygen pressure, reaching virtually constant value in intermediate pressures and increases at highest pressure range. Finally, these data as well as the results of kinetic rate measurements of Co_3±yO₄ formation have been utilized in calculating the chemical diffusion coefficient as a function of temperature.

Abstract: A variety of loadings of Cobalt oxide (Co₃O₄) was successfully supported on the reduced graphene (Co₃O₄/rGO) as the catalyst to activate peroxymonosulfate (PMS) to generate sulfate radicals (SO₄⁻•) for degrading Orange II in water. The crystal structure of Co₃O₄/rGO with different loadings was characterized by X-ray diffraction (XRD), and their catalytic activity was compared in the same conditions. The result showed that the catalyst has an optimum Co₃O₄ loading. Using the 70.7% loading of Co₃O₄ in Co₃O₄/rGO as the catalyst, 100% decomposition could be achieved within 4 min with 1 mM Orange II, 0.05g/L catalyst, and 10 mM PMS.

Abstract: Co₃O₄ multilayer nanosheets were synthesized by a hydrothermal method and a post annealing treatment process. The effect of solution concentration and ratio on the morphology of Co₃O₄ precursor was studied. The crystalline structure, morphology and elemental composition of Co₃O₄ multilayer nanosheets were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy technologies. When exposed to reducing gas such as ethanol, resistance of Co₃O₄ multilayer nanosheet sensor increases quickly, demonstrating that the Co₃O₄ multilayer nanosheets are p-type conductivity. For 100 ppm alcohol at 240 °C, the sensor response is as high as 32, indicating that the powder of Co₃O₄ multilayer nanosheets is a very promising low-powder gas sensing material.

Abstract: The Co₃O₄ nanoparticles were obtained from the precursor precipitated by CoCl₂ and NaHCO₃ via precipitation method, and were characterized by IR, XRD. The firing system of precursor was detected by TG-DSC, and the effects of temperature on grain size were investigated.

Abstract: Co₃O₄/NiO nanocomposite films were electrochemically synthesized on a ITO surface. The Co₃O₄/NiO nanocomposite films were characterized by energy-dispersive X-ray analysis (EDS) and scanning electron microscopy (SEM). The electrochromic properties of Co₃O₄/NiO nanocomposite films are investigated in an aqueous alkaline electrolyte (0.1M KOH) by means of transmittance, cyclic voltammetry (CV) and chronoamperometry (CA) measurements. The Co₃O₄/NiO nanocomposite films exhibit a noticeable electrochromism with reversible color changes, and fast switching speed (4.1 s and 3.6 s).

Abstract: Nanomaterials research has become a major attraction in the field of advanced materials research in the area of Physics, Chemistry, and Materials Science. Biocompatible and chemically stable magnetic metal oxide nanoparticles have biomedical applications that includes drug delivery, cell and DNA separation, gene cloning, magnetic resonance imaging (MRI). This research is aimed at the fabrication of magnetic cobalt oxide nanoparticles using a safe, cost effective, and easy to handle technique that is capable of producing nanoparticles free of any contamination. Nanostructured Cobalt oxide powder was prepared by sonication method using ultrasonicator. Effect of sonication for different time intervals, on the morphology of cobalt oxide nanostructures was extensively studied. The morphology of the nanorods were very much affected by the sonication time, it was found that with an increase in sonication time, the length of the nanorods seem to considerably increase at the same time an agglomeration effect comes in to action and the rods form bundle like structures. These cobalt oxide nanorods were characterized using X-ray Diffraction characterization (XRD) and it revealed a cubic structure. Weight percentage of cobalt oxide was confirmed by thermo gravimetric analysis (TGA).