Hiroyuki Yamaura

CO Sensing Property of Transition Metal Oxide-Loaded SnO2 in a Reducing Atmosphere

CO sensing properties of various transition metal oxide-loaded SnO2 sensors were investigated in a reducing atmosphere such as wet H2 gas. Among transition metal oxide-loaded SnO2 sensors used in the present study, CuO-loaded SnO2 sensor exhibited the highest sensor response to 1% CO in wet 50% H2 at around 150°C, while it showed no sensor response in dry 50% H2. From X-ray diffraction (XRD) analysis, CuO was reduced to metallic Cu in a reducing atmosphere at above 150°C. H2-temperature-programmed reduction (H2-TPR) and diffuse reflectance Fourier transform infrared (DRIFT-IR) spectroscopy measurements were carried out to discuss the sensor response mechanism.

Anode Performance of Ni/(CeO2)1-x(LnO1.5)x (Ln: Lanthanoids) in SOFCs Using Hydrocarbon Fuels

The anode performances of Ni/(CeO2)1-x(LnO1.5)x (Ln: La, Pr, Nd, Sm, Gd, and Yb) were investigated in direct-methane solid oxide fuel cells. Among the anodes tested in the present study, Ni/CeO2-Sm2O3 and Ni/CeO2-Yb2O3 composite anodes showed the relatively low anodic overpotential. The anodic overpotential of Ni(x wt%)/(CeO2)1-y(SmO1.5)y depended strongly on Ni content, while it less depended on Sm content. The catalytic activity of methane oxidation was measured for Ni/LnDC at 973 K and Ni/CeO2 and Ni/CeO2-Yb2O3 samples showed the high catalytic activity. This result suggests that the activity for the direct oxidation of methane by O2 is not main factor controlling the anodic overpotential in direct methane solid oxide fuel cell.

Effect of Supported Transition Metal on CO Sensing Performance Using SnO2 in Reducing Atmosphere

CO sensing properties of various transition metal oxide-loaded SnO2 sensors were investigated in a reducing atmosphere such as wet H2 gas. Among transition metal oxide-loaded SnO2 sensors used in the present study, 5wt%CuO-loaded SnO2 sensor exhibited the highest sensitivity to 1% CO in wet 50% H2 at around 150 °C, while it showed no sensitivity in dry 50% H2. From XRD analysis, CuO was reduced to metallic Cu in a reducing atmosphere at above 150 °C. H2-temperature-programmed reduction (H2-TPR) and diffuse reflectance fourier transform infrared (DRIFT-IR) spectroscopy measurements were carried out to discuss the sensor response mechanism.

Study on the Perovskite-type Oxide Cathodes in Proton-conducting SOFC

The cathode performances of perovskite-type oxide electrodes were investigated in the H2-O2 fuel cell with proton-conducting electrolyte. Among the perovskite-type oxides tested in the present study, La1-xSrxFeO3(LSFO) showed the best cathode performance. The cathode performances of LSFO depended on the Sr content and the heat-treatment temperature prior to electrochemical measurements. The cathode reactions of both LSFO and Pt electrodes are discussed briefly based on the cathode overpotentials measured as a function of oxygen partial pressure. Finally, the structure and the electrical conductivity of the proton-conducting ceramic film fabricated on LSFO electrode substrate are presented.