Experimental and Theoretical Investigation of Degradation Mechanisms by Particle Coarsening in SOFC Electrodes P. Tanasini 1,2 *, M. Cannarozzo 3 , P. Costamagna 3 , A. Faes 2,4 , J. Van Herle 2 , A. Hessler- Wyser 4 , and C. Comninellis 1 1 Group of Electrochemical Engineering (GGEC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland 2 Laboratory of Industrial Energy Systems (LENI), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland 3 Department of Chemical and Process Engineering, University of Genova, Via Opera Pia 15, IT-16145 Genova, Italy 4 Centre for Interdisciplinary Electron Microscopy (CIME), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland Received December 30, 2008; accepted April 19, 2009 1 Introduction Over the past few years, clean energy conversion has become increasingly important. On one hand, this is reflected by the establishment of several international agreements such as the Kyoto Protocol [1], and on the other hand, by an increasing public awareness concerning climate change and the greenhouse effect. Amongst the numerous ways to reduce the emissions of carbon dioxide and other pollutants, two of the simplest ones are the improvement in the efficiency of energy conversion devices and the adoption of zero-emission fuels such as hydrogen obtained from renewable resources. In applications where small or medium energy amounts are required, fuel cells are, currently, considered as a possible answer to such demands. Solid oxide fuel cells (SOFCs) are high-temperature operat- ing fuel cells (700–900 °C). They are constituted of ceramic or cermet electrodes separated by a dense membrane made of an ion-conducting ceramic [2]; high temperature is necessary to guarantee sufficient ionic conduction of the electrolyte and good activity of the electrodes. Operating at high temperature leads to a number of advantages: a high activity of the Ni used as anodic catalyst – [ * ] Corresponding author, pietro.tanasini@epfl.ch Abstract Performance degradation data obtained from single solid oxide fuel cells, tested at 850 °C with air and humidified H 2 and using Ni-YSZ anode supported cells, are presented here. Microscopic investigation is carried out on both anode and cathode to quantify variations in the morphology at different operation times. The comparison between the measurements on the cells and the SEM image analysis allows to conclude that there is no relationship between the initial cell activation and microstructural modifications of the electrodes. On the other hand, it was found that cell degradation is strictly related to the coarsening of Ni particles occurring in the anode. A theoretical analysis based on an electrode micro- model has been performed in order to compare the variation in performance, expected from particle size change, with the observed data. The model confirmed the conclusions of the experimental results. Keywords: Coarsening, Degradation, Image Analysis, Micromodel, Microstructure, Percolation, SOFC 740 © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim FUEL CELLS 09, 2009, No. 5, 740–752 ORIGINAL RESEARCH PAPER DOI: 10.1002/fuce.200800192