Formation Of Co3O4 Nanoparticles Research Articles

Synthesis of Self-Assembled rGO-Co3O4 Nanoparticles in Nanorods Structure for Supercapacitor Application

A simple hydrothermal process was used to design self-assembled Co3O4 nanoparticles in nanorod structure in the presence of graphene oxide as a template. The as-prepared Co3O4 sample in a loose powder form was calcined at 450 °C to get the well-crystalline phase of the same compound. The obtained Co3O4 powder sample was characterized by using the powder XRD and SEM. The XRD pattern shows totally nine distinct reflection peaks of (111), (220), (311), (222), (400), (422), (511), (440), and (533) planes. The most intense peaks were chosen to evaluate the structural parameters. The lattice parameters (a), volume (V), and density (ρ) of the samples are 8.09 A, 529.47 A3, 6.06 g/cc, which are comparable to the value of lattice parameter (a = 8.056 A), volume (V = 528.30 A3), and density (ρ = 6.055 gm/cc) for bulk Co3O4. The average size of the Co3O4 nanoparticles is 14 nm which is smaller than the SEM size of 50 nm corresponding to the agglomeration of tiny particles. Further, the formation of Co3O4 nanoparticles were also confirmed by obtaining the band at 569, 1334,1337, 1566, and 3397 cm−1 in FTIR spectrum. Totally five characteristics peaks from Co3O4 at 182.57, 456.49, 505.84, 605.80, and 618.02 cm−1 and peaks from GO-Co3O4 at 182.57, 483.44, 505.84, 605.80, and 618.02 cm−1 corresponding to F2g, Eg, F2g, F2g, and Ag modes of the crystalline Co3O4, respectively, in the Raman spectra. In the case of GO-Co3O4 composite, low-intensity peaks of D and G bands are observed. The specific capacitance in rGO-Co3O4 nanocomposite is about 65.15 Fg−1.

Effects of the SrTiO3 support on visible-light water oxidation with Co3O4 nanoparticles.

The photocatalytic activity of SrTiO3 modified with Co3O4 nanoparticles for water oxidation under visible light (λ > 480 nm) was investigated with respect to the physicochemical properties of the SrTiO3 support. SrTiO3 was synthesized by a polymerized complex method or a hydrothermal method, followed by calcination in air at different temperatures in order to obtain SrTiO3 particles having different sizes. Co3O4 nanoparticles, which provide both visible light absorption and water oxidation centers, were loaded on the as-prepared SrTiO3 by an impregnation method using Co(NO3)2 as the precursor, followed by heating at 423 K in air. Decreasing the SrTiO3 particle size (that is, improving the crystallinity) enhanced the photocatalytic activity by promoting the formation of Co3O4 nanoparticles that provided optimal light absorption and catalytic sites. However, Co3O4 aggregation occurred on overly large SrTiO3 particles, leading to a decrease in activity. This study demonstrates the possibility of tuning the photocatalytic activity of a Co3O4-loaded wide-gap semiconductor for visible light water oxidation through the appropriate selection of the support material.

Supercritical CO2-Mediated Synthesis of CNT@Co3O4 Nanocomposite and Its Application for Energy Storage

Carbon nanotubes (CNT)/cobalt oxide (Co3O4) nanocomposites were synthesized using a facile one-step solvothermal method in supercritical carbon dioxide. The formation of Co3O4 nanoparticles on the surface of the CNTs was confirmed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The analyses revealed the surface of the CNTs to be coated uniformly with Co3O4 nanoparticles with a mean size of ca. 5 nm. The electrode-modified CNT/Co3O4 composites exhibited a high specific capacitance of 950 F g–1 at a current density of 1 A g–1 as well as excellent cycling stability (94.6% capacitance retention after 2000 cycles).

Synthesis and optical properties of cubic Co3O4 nanoparticles via thermal treatment of a trinuclear cobalt complex

Cubic cobalt oxide nanoparticles with the formula of Co3O4 were synthesized via thermal treatment in air, using [CoII{(µ-L)(µ-OAc)CoIII(NCS)}2]; [H2L=salen=1,6-bis(2-hydroxyphenyl)-2,5-diazahexa-1,5-diene]; as precursor. Effect of calcination temperature and citric acid, as emulsifier, was investigated on the phase formation and particle size distribution of the products. Calcination of the precursor at 600°C in the presence of citric acid results in the formation of Co3O4 nanoparticles with the average crystallite size of ∼13nm. The presence of citric acid provides conditions for the formation of more pure Co3O4 crystalline phase with smaller particles. The as-prepared nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), particle size analyzer (PSA), transmission electron microscopy (TEM), UV–vis and Photoluminescence (PL) spectroscopies. The optical property studies indicate that the absorption peaks of Co3O4 nanoparticles, prepared in the presence of citric acid, shift towards short wavelengths. This blueshift is related to the quantum size effect.

Synthesis and spectroscopic investigation of cobalt oxide nanoparticles

Hydroxyethyl cellulose and cobalt chloride are used as precursor materials for the synthesis of cobalt oxide (Co3O4) nanoparticles. A composite system from polymer and metal chloride is prepared via casting technique. The thermal decomposition of the composite is studied using thermogravimetric technique. Calcination of the composite system at 350°C resulted in the formation of Co3O4 nanoparticles. X‐ray diffraction analysis reveals the presence of crystalline Co3O4 with an average particle size of around 15 nm. The bonding nature and morphology of nanosized Co3O4 are examined using transmission electron microscopy and infrared spectroscopy. The Tauc's plot indicates the energy band gap for direct allowed transition as 3.2 eV and 1.4 eV. POLYM. COMPOS., 37:1881–1885, 2016. © 2015 Society of Plastics Engineers

Fabrication and electrochemical properties of copper oxide (CuO) nanowire–cobalt oxide (Co3O4) nanoparticle heterostructures for oxygen evolution reaction

Nanoscale heterostructures of metal oxides with controlled morphology, interface and phase purity have been considered of great importance for efficient and cost-effective water splitting process. Here, we report the fabrication of CuO nanowire–Co3O4 nanoparticle heterostructures for the oxygen evolution reaction in the electrocatalytic water splitting process. The synthesis was achieved in a facile and surfactant-free two-step thermal growth process, where free-standing CuO nanowires were first produced by directly annealing a piece of copper foil in the air. This was followed by dip-coating of cobalt salt on the surface of CuO nanowires and subsequent thermal treatment in air to result in the uniform formation of Co3O4 nanoparticles on the CuO nanowires. The morphology and structure of the heterostructures were characterised by the microscopic and diffraction methods. CuO nanowires or the heterostructures were further coated onto a glassy carbon electrode for oxygen evolution in the electrochemical water splitting. The effective surface areas of the electrodes were measured using the Randles–Sevcik equation. Their electrocatalytic activity was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel methods.