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Anodic Layers Based on Doped-Ceria/Ni Cermet for Direct Ethanol Fuel Cells

Friday, 28 July 2017: 11:00
Grand Ballroom West (The Diplomat Beach Resort)
A. A. A. da Silva (INT, IME), F. N. Tabuti (IPEN), L. V. Matos (UFF), M. C. Steil (Université Grenoble Alpes, CNRS, LEPMI), F. B. Noronha (INT), and F. C. Fonseca (IPEN-CNEN/SP)
Latest generation of solid oxide fuel cells (SOFCs) is a multilayer device in which several functional layers were incorporated to the anode/electrolyte/cathode configuration. Therefore, using an active layer that enables the fuel cell to run using a renewable fuel such as bioethanol is a reasonable strategy. Separating the catalytic and electrochemical reactions in different anodic layers has two main advantages: keeping the high-performance YSZ/Ni cermet and allowing an active and stable catalyst for ethanol reforming. Doped-cerium oxide is an attractive ceramic material for solid oxide fuel cells (SOFCs) because of the excellent electrochemical and catalytic properties and good compatibility with remaining cell components. In the present study, we have investigated the effect of different dopants on the properties of doped-ceria in Ni cermets aiming at using such cermets as the catalyst for ethanol internal reforming in SOFCs. High surface area ceria doped (10 mol%) with Gd, Y, Zr, and Nb were prepared by an hydrothermal method. The ceria-based solid solutions were mixed with Ni by a wet impregnation method to obtain 18 wt.% Ni relative fraction. Such relatively low Ni volume fraction (~15 vol.%) aims at minimizing coke formation while promoting electronic conductivity. The catalyst materials were deposited onto the anode of standard electrolyte-supported cells [(La,Sr)xMnO3 / YSZ / YSZ/Ni] and tested on dry ethanol. The fuel cell tests results were analysed along with data of both steam reforming and decomposition catalytic reactions for ethanol. Post-test analyses evidenced that water electrochemically generatedpromotes ethanol reforming, in agreement with catalytic tests in which doped-ceria/Ni showed no evidence of carbon deposits in the steam reforming reaction. On the other hand, analyses on spent catalysts of ethanol decomposition revealed carbon deposits. Nevertheless, no significant differences were observed for the studied dopants with the notable exception of niobium, which has a limited solubility in the ceria matrix. The experimental results confirm that upon fuel cell operation, ceria-Ni based catalysts promote alcohol steam reforming resulting in stable direct ethanol SOFCs.