In situ XANES Studies on Ce0.9Zr0.1-xSmxO2-x/2 (x= 0.1, 0.08, 0.06, 0.04, 0.02, 0) synthesized by hydrothermal method

ROSARIO SUAREZ ANZORENA; MUÑOZ, FERNANDO F.; L. M. TOSCANI; S.A. LARRONDO.

Encuentro; 30th RAU Annual Users Meeting; 2020

60%NiO/Ce0.9Zr0.1O2 has demonstrated to be an excellent anode material for Intermediate Temperature-Solid Oxide Fuel Cells. Nevertheless, its mixed conductivity should be enhanced in reducing atmospheres [1]. The substitution of Zr4+ by Sm3+ is proposed to incorporate oxygen vacancies into the structure thus improving ionic conductivity. Ce0.9Zr0.1-xSmxO2-x/2 (x= 0.1, 0.08, 0.06, 0.04, 0.02, 0) mixed oxides were synthesized via the hydrothermal method and calcined at 550 °C. X-ray diffraction with synchrotron radiation shows that all samples are monophasic with the fluorite structure, typical of CeO2. Average crystallite sizes are nanometric (< 11 nm) and lattice parameters increases linearly with Sm3+ content. The effect of Sm3+ incorporation into the lattice on redox properties was studied by in situ Dispersive X-ray absorption spectroscopy (DXAS) experiments, performed in diluted H2 gas-flow (5 vol.% in 50 mL.min-1, He balance), from room temperature to 800 ºC with a heating rate of 10 ºC.min-1. DXAS measurements were performed at the Ce LIII absorption edge, being this spectroscopy especially suited for tracking time-dependent evolution of chemical reactions. Three reduction steps were observed during the process, two of which can be related to the reduction of surface Ce4+ species (< 600 °C) and the third one to the reduction of bulk species. The incorporation of Sm3+ increased the reduction kinetics of bulk species. The exit gas is analyzed by online mass spectroscopy. Water production was observed in accordance with each reduction step.