In-situ DXAS study of NiO/CeO2-Gd2O3 nanocomposites forIT-SOFC anodes

M. BELLORA; PAULA M. ABDALA; M. SUAREZ ANZORENA; R.BACANI; S.A. LARRONDO.; R.J. PRADO; D.G. LAMAS

Campinas

Encuentro; 23º Reunión Anual de Usuarios (RAU),; 2013

CNPEM

Fuel cells are promising devices for environmentally clean energy production by directly converting chemical energy into electricity. Among them, solid oxide fuel cells (SOFCs)have the unique capability to use different fuels such as hydrocarbons or H2. However,several issues have to be solved in order to improve their efficiency and reduce their costs. The reduction of their working temperature, which is typically around 900- 1000oC, is one of the most important issues. For this reason, extensive research has been devoted to develop novel materials for intermediate-temperature SOFCs (IT-SOFCs). CeO2-based anodes have proven to exhibit excellent catalytic properties. Besides, these materials are mixed ionic/electronic conductors (MIECs) under reducing atmosphere and, therefore, fuel oxidation can take place on its entire surface, while it only oc-curs in the [anode/electrolyte/gas] interphase (triple-phase boundaries) for electronic conductors. In recent works, we investigated the performance of nanostructured CeO2-based anodes for IT-SOFCs. Nanomaterials are not employed in conventional SOFCs since grain growth is expected to occur at high temperature, but their use in IT-SOFCs is currently under evaluation. Anodes based on nanostructured MIECs are very interesting because the number of active sites for fuel oxidation is expected to increase dramatically. For example, we have found that NiO/GDC (GDC: Gd2O3-doped CeO2) nanocomposites exhibit excellent performance under H2, with enhanced properties with decreasing grain size. The aim of this work was to study the influence of the crystallite size on the reducibility of NiO/GDC nanocomposites under diluted H2 by the DXAS technique.We found that NiO/GDC nanocomposites of smaller crystallite size exhibit much higher reducibility for both Ni and Ce atoms, which is probably related to the excellent performance of nanostructured NiO/GDC anodes.