Attera Worayingyong

Determination of phase ratio in polymorphic materials by x-ray absorption spectroscopy: The case of anatase and rutile phase mixture in TiO2

We demonstrate that x-ray absorption spectroscopy (XAS) can be used as an unconventional characterization technique to determine the proportions of different crystal phases in polymorphic samples. As an example, we show that ratios of anatase and rutile phases contained in the TiO2 samples obtained by XAS are in agreement with conventional x-ray diffraction (XRD) measurements to within a few percent. We suggest that XAS measurement is a useful and reliable technique that can be applied to study the phase composition of highly disordered or nanoparticle polymorphic materials, where traditional XRD technique might be difficult.

Electrochemical Properties of Zinc-LaCoO3 Electrode for Alkaline Zinc-Based Battery

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.

Promoted and Un-Promoted Co/SiO2 Fischer-Tropsch Catalysts

Un-promoted and promoted Co/SiO2 catalysts with ZrO2 and Ru were prepared and the catalytic performances for Fischer-Tropsch synthesis were investigated. The prepared catalysts were characterized by XRD, N2 adsorption/desorption, and X-ray absorption techniques. XRD suggested that the cobalt species presence in all prepared catalysts was Co3O4. Promoted catalyst with ZrO2 and Ru showed high distribution of cobalt on silica surface resulted in smaller Co3O4 crystalline size than un-promoted ones. From the reaction testing, the obtained products of C1 to C9 from un-promoted and promoted Co/SiO2 were studied.

Effect of LaCoO3 Additive on the Electrochemical Behavior of Zinc Anode in Alkaline Solution

The utilization of zinc anode for zinc-based battery is limited due to low cycling life, shape change and ZnO passivation on the electrode surface. The electrochemical behavior of zinc anode in the presence of the additives added to the electrodes or the electrolytes have been reported. In this work, LaCoO3 was used as an additive to improve the electrochemical properties of the zinc oxide anode. LaCoO3 synthesized by sol gel method (Schiff base complex) was added to zinc oxide powder (99.9%) with the weight ratio of 1:0.001, 1:0.002 and 1:0.003. The relative ZnO/LaCoO3 ratios were confirmed by particle induced x-ray emission (PIXE) technique.The electrochemical behavior of the ZnO/LaCoO3 electrodes in 6M KOH solution were investigated by voltammetry and electrochemical impedance spectroscopy (EIS). The cyclic voltammogram showed that ZnO/LaCoO3 gave higher anodic current and ZnO passivation delayed. The EIS spectra showed that charge transfer resistances of the ZnO/LaCoO3 anodes due to zinc oxidation were higher than that of ZnO electrode

Carbon Black-LaCoO3 Composite Material as Counter Electrode for Quasi-Solid-State Dye-Sensitized Solar Cell

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.