Nanostructured Cathodes for Solid Oxide Fuel Cells by a Solution Spray-Coating Process

Abstract

Composite nano-cathodes containing Sr-doped LaMnO 3 (LSM) and Gd 2 O 3 -doped CeO 2 (GDC) were deposited on yttria-stabilized zirconia (YSZ) discs and YSZ/NiO + YSZ bi-layer discs using an aqueous solution. The samples were heated over a range of temperatures from 700°C to 1200°C to form LSM + GDC porous films. The crystallite size was estimated using X-ray diffraction (XRD) Scherrer formula. The crystallite size was in the ~3 nm to ~80 nm range. Polarization resistance was measured by electrochemical impedance spectroscopy (EIS) from 400°C to 700°C. Nano-cathodes of ~70 nm thickness fired at 700°C exhibited polarization resistance of ~0.23 Ωcm 2 at 700°C. By contrast, LSM + YSZ cathodes made by a conventional process exhibited polarization resistance of ~2 Ωcm 2 . Fuel cell tests were conducted at 700°C on cells with nano-cathodes and conventional LSM + YSZ cathode. The maximum power density was ~0.51 Wcm –2 with nano-cathodes. By contrast, the corresponding power density with conventional LSM + YSZ cathodes was ~0.11 Wcm –2 . Here, the present work shows that very thin cathode functional layers can be deposited on sintered YSZ/NiO + YSZ bi-layer discs by using an aqueous solution. This approach in principle could be extended to large area cells.