High electrode activity of nanostructured, columnar ceria films for solid oxidefuel cells

Abstract

Highly porous oxide structures are of significant importance for a wide variety of applications in fuel cells, chemical sensors, and catalysis, due to their high surface-to-volume ratio, gas permeability, and possible unique chemical or catalytic properties. Here we fabricated and characterized Sm_0.2Ce_0.8O_1.9−δ films with highly porous and vertically oriented morphology as a high performance solid oxide fuel cell anode as well as a model system for exploring the impact of electrode architecture on the electrochemical reaction impedance for hydrogen oxidation. Films are grown on single crystal YSZ substrates by means of pulsed laser deposition. Resulting structures are examined by SEM and BET, and are robust up to post-deposition processing temperatures as high as 900 °C. Electrochemical properties are investigated by impedance spectroscopy under H₂–H₂O–Ar atmospheres in the temperature regime 450–650 °C. Quantitative connections between architecture and reaction impedance and the role of ceria nanostructuring for achieving enhanced electrode activity are presented. At 650 °C, pH₂O = 0.02 atm, and pH₂ = 0.98 atm, the interfacial reaction resistance attains an unprecedented value of 0.21 to 0.23 Ω cm² for porous films 4.40 μm in thickness.