Nanostructured Cu-CeO2/YSZ cermet for SOFC anodes: effect of sintering temperature on the mesostructure and polarization

SÁNCHEZ FABA, E.M.; JESUS E. VEGA CASTILLO; HORACIO TROIANI; LILIANA MOGNI; CHANQUIA CORINA M.

C.A.B.A.

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

Asociación Argentina de Ingenieros Químicos

The development of new C-tolerant anodes is fundamental to improving stability in direct hydrocarbon-fueled solid oxide fuel cells (SOFC). In this work, a Cu-CeO2/YSZ cermet developed from the infiltration of mesoporous yttria-stabilized zirconia (YSZ) was studied with this purpose, focusing on the impact of the sintering temperature on its mesostructure and electrochemical behavior. Mesoporous YSZ was successfully prepared by a sol-gel process followed by hydrothermal treatment. A detailed morphological and structural characterization was performed, employing X-ray diffraction, nitrogen physisorption, and electron microscopy (scanning and transmission). The synthesized material consists of interconnected nanocrystallites of about 7 nm, forming a “wormhole-like” mesoporous architecture. The as-synthesized YSZ was used to build symmetrical cells by spin-coating on dense TZ-8Y electrolytes. The electrode scaffolds were obtained due to a thermal treatment at 950, 1150, and 1350 °C for 1 h, with the consequent increase of the grain size and decrease of the BET-specific surface. Then, the electrodes were infiltrated with 30 wt% of Cu and 10 wt% of CeO2 to produce a mixed conductor and active sites for fuel oxidation. Electrochemical impedance spectroscopy measurements made at 700 °C in a wet methane atmosphere evidenced that the microstructural differences produced by the variations in the thermal treatments impact the polarization resistance: a higher sintering temperature improves the contact between the ceramic particles, favoring the transport of oxygen ions, and reducing the resistance of the cell. Thus, the cells sintered at 1350 °C maintained a stable behavior throughout the exposure time. An enhanced electrode was fabricated by uniaxial pressing the mesoporous YSZ and treated for 12 h at 1350 °C. By following this method, the anode polarization resistance is reduced by one order of magnitude.