Thin Films Of Co3O4 Research Articles

“Intelligent” Pt Catalysts Based on Thin LaCoO3 Films Prepared by Atomic Layer Deposition

LaCoO3 films were deposited onto MgAl2O4 powders by atomic layer deposition (ALD) and then used as catalyst supports for Pt. X-ray diffraction (XRD) showed that the 0.5 nm films exhibited a perovskite structure after redox cycling at 1073 K, and scanning transmission electron microscopy and elemental mapping via energy-dispersive X-ray spectroscopy (STEM/EDS) data demonstrated that the films covered the substrate uniformly. Catalysts prepared with 3 wt % Pt showed that the Pt remained well dispersed on the perovskite film, even after repeated oxidations and reductions at 1073 K. Despite the high Pt dispersion, CO adsorption at room temperature was negligible. Compared with conventional Pt on MgAl2O4, the reduced forms of the LaCoO3-containing catalyst were highly active for the CO oxidation and water gas shift (WGS) reactions, while the oxidized catalysts showed much lower activities. Surprisingly, the reduced catalysts were much less active than the oxidized catalysts for toluene hydrogen. Catalysts prepared from thin films of Co3O4 or La2O3 exhibited properties more similar to Pt/MgAl2O4. Possible reasons for how LaCoO3 affects properties are discussed.

Stainless steel grid mesh-supported CVD made Co3O4 thin films for catalytic oxidation of VOCs of olefins type at low temperature

The effective evaluation of the catalytic performance of Co3O4 supported on an inert carrier was investigated toward the deep oxidation of light olefins. Thin Co3O4 films were deposited on grid mesh of stainless steel using one-step chemical vapor deposition method. The as-deposited materials were characterized in terms of structure, morphology and composition. Co3O4 crystals with cubic spinel structures composed of Co2+, Co3+ and nucleophilic oxygen species (O2−) were obtained. The catalytic results indicated that Co3O4 supported on steel mesh was highly active to enable the complete conversion of C3H6 and n-C4H8 with a Mars-van Krevelen type mechanism.

ChemInform Abstract: Thin Films of Co3O4 and NiCo2O4 Prepared by the Method of Chemical Spray Pyrolysis for Electrocatalysis. Part 4. The Electrocatalysis of Oxygen Reduction.

ChemInform Abstract: Thin Films of Co3O4 and NiCo2O4 Prepared by the Method of Chemical Spray Pyrolysis for Electrocatalysis. Part 4. The Electrocatalysis of Oxygen Reduction.

Thin films of Co3O4, MnCo2O4 and their solid solution as electrocatalyst: study of their magnetic properties

We present magnetic measurements performed on the MnxCo3–xO4 (0 ≤ x ≤ 1) solid solution, prepared by spray pyrolysis. Thin films of about 20 μm thickness were obtained after depositing aqueous metal nitrates precursors on Ti or conducting glass substrates. Powder material scratched from the substrate's surface was used for physico-chemical characterization. Presence of two oxidation states for each metal ion (Mn3+–Mn4+; Co2+–Co3+) triggers specific conduction mechanisms and double-exchange magnetic interactions. The ferromagnetic components are enhanced when x(Mn) increases, in detriment of the antiferromagnetic interactions. The ordering temperature Tc changes with x (from 22 K up to room temperature, for x = 0 up to x = 1). Based in the paramagnetic moment μeff obtained at T > Tc, we propose a cationic distribution which can be nicely compared to the one obtained from crystallographic analyses. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Epitaxial Growth of Co3O4 Films by Low Temperature, Low Pressure Chemical Vapor Deposition

ABSTRACTThe growth of strongly oriented or epitaxial thin films of metal oxides generally requires relatively high growth temperatures or infusion of energy to the growth surface through means such as ion bombardment. We have grown high quality epitaxial thin films of Co3O4 on different substrates at a temperature as low as 450°C by low-pressure metal-organic chemical vapor deposition (MOCVD) using cobalt(II) acetylacetonate as the precursor. With oxygen as the reactant gas, polycrystalline Co3O4 films are formed on glass and Si(100) in the temperature range 350-550°C. Under similar conditions of growth, highly oriented films of Co3O4 are formed on SrTiO3(100) and LaAlO3(100). The film on LaAlO3(100) grown at 450°C show a rocking curve FWHM of 1.61°, which reduces to 1.32° when it is annealed in oxygen at 725°C. The film on SrTiO3(100) has a FWHM of 0.330 (as deposited) and 0.29° (after annealing at 725°C). The ø-scan analysis shows cube-on-cube epitaxy on both these substrates. The quality of epitaxy on SrTiO3(100) is comparable to the best of the pervoskite-based oxide thin films grown at significantly higher temperatures.

Thin films of Co3O4 and NiCo2O4 obtained by the method of chemical spray pyrolysis for electrocatalysis III. The electrocatalysis of oxygen evolution

The electrocatalytic properties of thin Co3O4 and NiCo2O4 films prepared on CdO-nonconductive glass by the method of chemical spray pyrolysis were investigated for oxygen evolution in varying KOH concentrations. The Tafel slopes were close to (2.3RT/F) V per decade for both oxides. The reaction order with respect to [OH−] was found to be approximately 1.3. It was observed that Co3O4 is more active than NiCo2O4 towards oxygen evolution. A mechanism for oxygen evolution involving the electrochemical adsorption of OH− as a fast step and the electrochemical desorption of OH forming an intermediate H2O2 as the rate-determining step has been suggested.