XANES study of the oxidation state of Cu, Ni and Ce cations in the Cu-Ni/Ce0.9Zr0.1O2 cermet in reducing atmospheres

TOSCANI L.M.; M.G. ZIMICZ; TEREZA MARTINS; D.G. LAMAS; LARRONDO S.A.

Congreso; 25th Annual Users? Meeting, RAU (Reunion Anual de Usuarios del Laboratorio Nacional de Luz Sincrotron, Brasil); 2015

Solid Oxide Fuel Cells stand as a promising technology for efficient and sustainable energy production. In this context, ce{Ce_{0.9}Zr_{0.1}O2} (Ni/ZDC) cermets are an excellent alternative to Ni/YSZ commercial anodes. The aim of this work is to study the effect of partial substitution of Ni by Cu in that cermet and to evaluate its performance in redox and catalytic conditions. In situ XANES experiments using synchrotron radiation were performed at the Ce-LIII, Cu-K and Ni-K edges. Temperature programmed reduction (TPR) experiments were carried out in 5 mol.% ce{H2}/He atmospheres. Ce-LIII edge resultsshowed Ni/ZDC and CuNi/ZDC almost identical profiles up to 670°C, while the bimetallic sample presented higher reduction percentages up to 800°C. Both samples concluded the experiment with a total 40% of Ce reduction. In the Ni-K edge, the bimetallic sample presented a lower reduction onset temperature and a higher proportion of Ni surface species exhibited in the larger area under first peak of TPR profile, with 100% Ni reduction in both cases. Cu-K edge results showed a two step Cu reduction for the bimetallic sample. When the cermets are exposed to ce{CH4}:ce{O2}=2.6 ratio atmosphere, they exhibited low catalyst reduction percentages: 8% Ni reduction for both cermets, 4% and 2% Ce reduction for cermets containing Ni and CuNi, respectively. The mass spectrometer signals of the exhaust gases during the experiments showed the production of both ce{H2} and CO for temperatures above 650°C.