Papers by Keyword: LaCoO₃

Abstract: Porous materials are attractive in various applications such as energy storage and production, industrial processing, environmental treatment, and catalysis. Porous LaCoO₃ was prepared using three different metal precursor solutions: i) 40%v/v methanol-ethylene glycol (40%Me/EG), ii) Lysine (Lys), and iii) Lysine/citric acid (Lys/Cit) with poly(methyl methacrylate) colloidal crystal as porous templates (PMMA-CCT). PMMA-CCT filled with metal precursor solution were carbonized under N₂ followed by oxidized under 50% O₂ in N₂ atmosphere. X-ray diffraction patterns of the obtained porous LaCoO₃ are rhombohedral LaCoO₃ phase without impurity. The scanning electron microscopy (SEM) was carried out to examine the morphology of porous LaCoO_3. The SEM image of the LCO-Lys/Cit exhibits better connected particles and a well-defined pore structure compared to those prepared by Lys or 40%Me/EG metal precursor solutions. The evolution of pore formation of LCO-Lys/Cit was investigated by SEM, Fourier transform infrared spectroscopy (FT-IR), and thermal gravitational analysis (TGA). The materials show high catalytic properties for the electrochemical water oxidation reaction. The high capacitances of all porous LaCoO₃ are attributed to the controlled three-dimensional porous morphology of the catalysts. This synthesis approach can achieve porous materials with promising properties for catalysis applications.

Abstract: Chemical reactivity and cathode properties of LaCoO₃ were investigated using new oxide ion conductor, lanthanum silicate oxyapatite. The LaCoO₃ is found to be good candidate for cathode of the lanthanum silicate oxyapatite solid-electrolyte since no chemical reaction occurred between the LaCoO₃ and lanthanum silicate oxyapatite heating at 1273 K for 60 h in air. Based on electrochemical measurements, lower overpotential between the LaCoO₃ and lanthanum silicate oxyapatite was confirmed compared to the overpotential at YSZ/LaCoO₃ interface. From analysis on the extended interfacial conductivity as function of oxygen activity at the triple phase boundary at fixed temperature, the overpotential evaluated by impedance spectra is the rate limiting process by oxygen diffusion on the LaCoO₃ surface. Comparing to the bulk conductivity of LaCoO₃, the electrode resistance evaluated by impedance spectra was confirmed to be different from the electrical transport properties of the LaCoO₃ bulk.

Abstract: This paper reports results of dodecane-sensing studies with double-substituted LaCoO₃ perovskite oxide nanowires. La_0.40Sr_0.15Ag_0.45CoO_3-α nanowires were co-sputtered from metallic La, Sr, Ag and Co targets in the presence of a reactive argon-oxygen gas mixture. As deposited coatings are amorphous and crystallise in the perovskite structure after annealing at 873 K for 2 hours under air. Electrical response of the La_0.40Sr_0.15Ag_0.45CoO_3-α nanowires was measured at different temperature under air and under air containing 1 to 100 ppm (v) of dodecane vapour. The electrical signal of the nanowires was found to be high and it was possible to detect low concentrations of dodecane (under 5 ppm (v) ) at 573 K.

Abstract: The electrochemical behaviors of zinc anode in the presence of the additives added to the electrodes are presented. LaCoO₃ was used as an additive to improve the electrochemical properties of the zinc anode. LaCoO₃ synthesized by sol gel method (Schiff base complex) was added to Zn and ZnO powder with the weight ratios of 1:0.05 and 1:0.002 respectively. The electrochemical properties of the zinc and zinc/LaCoO₃ electrodes in 6M KOH solution were investigated by voltammetric technique and electrochemical impedance spectroscopy (EIS). The cyclic voltammograms showed that zinc electrodes with LaCoO3 additive gave higher anodic currents and ZnO passivation delayed. The cathodic Tafel plot indicated that the hydrogen overpotential shifted toward more negative value. The EIS revealed that the charge transfer resistances of the zinc/LaCoO₃ electrodes were higher than that of zinc electrodes.

Abstract: Using La₂O₃ and Co(NO₃)₂•6H₂O as raw material, ultrafine perovskite-type oxides LaCoO₃ was prepared by Supercritical Fluid Drying Technology and Sol-Gel method. The prepared materials’ crystal structure and morphology were characterized by TG-DTA、XRD、FT-IR and TEM. The photocatalytic activity of ultrafine LaCoO₃ powders was evaluated by degradation of methyl orange (MO) solution under 15W UV light irradiation. The results show: At 250°C , the amorphous ultrafine La-Co particles with the size less than 10 nm can be obtained by Supercritical Fluid Drying Technology. At 850°C , the size of the particles increased to 15-35nm, the nanocrystalline LaCoO₃ had a perfect rhombohedral perovskite structure. At 900°C , the crystalline phases of the lanthanum-cobalt mixed oxides were LaCoO₃ and La₂O₃, and the amorphous component is Co₂O₃, the presence of lanthanum affects the crystallization of cobalt oxides. The LaCoO₃ has excellent photocatalytic activities and 100% MO solution was decolorized only after 4h.

Abstract: Dye-sensitized solar cell (DSSC) is considered as the next generation low cost photovoltaic device, and one of the important components is the counter electrode which reduces the I3- ions generated after electron injection from iodide into the oxidized sensitizer. In this work composite material of carbon black and LaCoO3 synthesized by sol-gel method has been investigated to replace the platinized counter electrode for quasi-solid-state dye-sensitized solar cells. From cyclic voltammogram, it was found that carbon black catalyzed with LaCoO3 exhibited increased reduction current compared with that of carbon black without LaCoO3. This was consistent with increased surface roughness depicted from scanning electron microscopy (SEM) image. The electrochemical impedance spectroscopy (EIS) of DSSCs using carbon black-LaCoO3 composite as counter electrode revealed lower charge-transfer resistance (Rct) than that using carbon black. The highest conversion efficiency of 5.40% was obtained from DSSC (active area 1 cm2) fabricated with quasi-solid composite polymer electrolyte using carbon black-LaCoO3 (95:5 ratio by weight) compared to 5.23% obtained from DSSC equipped with platinum counter electrode. The performances of the quasi-solid-state DSSCs sensitized with N719 and natural dyes were examined and it was concluded that the carbon black-LaCoO3 composite was compatible with platinum coated counter electrode for DSSCs.