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

Abstract

Composite nano-cathodes containing Sr-doped LaMnO3 (LSM) and Gd2O3-doped CeO2 (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 Ωcm2 at 700°C. By contrast, LSM + YSZ cathodes made by a conventional process exhibited polarization resistance of ∼2 Ωcm2. 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. 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.