CuFe bimetallic nanoparticles were prepared and used as model catalyst for deactivation study in higher alcohol synthesis. The structural evolution of CuFe bimetallic nanoparticles during reaction was investigated. Phase separation of Cu and Fe components was observed directly by STEM-EDS and HRTEM. It was found that CuFe bimetallic nanoparticles with homogeneous dispersion of Cu and Fe components separated into monometallic Cu nanoparticles, Fe3O4 nanoparticles, Fe3O4 nanorods and chi-Fe5C2 in the form of very small crystallites or amorphous layer on Fe3O4 containing nanoparticles and nanorods. The phase separation weakened the synergism between Cu and Fe and led to decreased selectivity to alcohols with time on stream. The correlation between the change of catalytic performance and the structural evolution was also discussed. (c) 2013 Elsevier B.V. All rights reserved.