CONICET | Buscador de Institutos y Recursos Humanos

In light of developing efficient anodes for intermediate temperature solid oxide fuel cells (IT-SOFC), materials with mixed ionic-electronic conductivity and excellent redox properties are sought-after. The main objective of this work is to study the effect of temperature and fuel composition (H2 or CH4) in the reducibility of Ce-Sc-Zr-O mixed oxides in reducing atmospheres. Samples were synthesized using two different routes, namely glycine/nitrate combustion route (GC) and citrate complexation route (CIT). Samples were prepared with the following compositions: Ce0,9ScxZr0,1-xOδ, with x=0; 0.02; 0.04; 0.06; 0.08 y 0.1 and fired at 500°C. Furthermore, some selected samples with superior catalytic and electrocatalytic performance at conventional laboratory experiments were fired at 800°C and/or at 1000°C and impregnated with CuO-NiO. In-situ DXAS experiments were performed at the Ce LIII-edge of the D06A-DXAS dispersive beam line of the LNLS. Temperature programmed reduction (TPR) experiments were performed by heating the samples in a flow of diluted H2 or diluted CH4 from room temperature to 800°C. From in-situ DXAS experiments we concluded that CeO2-ZrO2-Sc2O3 samples prepared by both CIT and GC routes and fired at 500°C exhibited a superior Ce redox behavior than CeO2-ZrO2 and CeO2-Sc2O3 samples in the temperature range of 500°C-800°C, temperature range of interest for IT-SOFC applications. Sc-doped and non-doped samples fired 1000°C exhibited a similar redox behavior in H2, whereas in CH4 atmosphere, 4 at.% Sc sample exhibited higher Ce reduction values when impregnated with CuO-NiO, indicating that oxygen vacancy generation through aliovalent doping promotes Ce reduction when CuO-NiO is added to the system. This improved redox capacity is highly desirable when NiO is present in the system as it can prevent catalyst deactivation from carbon deposition by delivering oxygen from its lattice to gasify carbonaceous species