Herein, Cr deposition and poisoning behavior at the commonly used (La0.6Sr0.4)(Co0.2Fe0.8) O3-delta (LSCF) electrode of solid oxide fuel cells (SOFCs) is investigated. Three-dimension (3D) microstructure evolution of the porous electrode caused by Cr deposition during the polarization test at 900 degrees C in the presence of a Fe-Cr metallic interconnect is characterized for the first time using the transmission X-ray microscopy (TXM) technique. The results indicate that a layer of solid Cr deposits similar to 1.7 mu m in thickness is formed on the electrode surface, significantly reducing the linear porosity to similar to 2% in the surface region from similar to 25% in the bulk, which explains the retarded gas diffusion process at the LSCF electrode after Cr deposition. The well-established relationship between the macroscopic performance degradation and the microstructure evolution confirms the promising application of TXM technique for in-depth study of the degradation phenomenon at the electrode of SOFCs. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.