Palladium nanoparticles were successfully immobilized on the surface of magnetic γ-Fe_2O_3 nanoparticles by the sonochemical reduction method. HAADF-STEM observation showed that the size of the immobilized palladium nanoparticles were several nanometers. The Pd/γ-Fe_2O_3 composite nanocatalysts exhibited high catalytic activity for nitrobenzene reduction, and formed aniline with high selectivity and high turn over frequencies. In addition, after several reuse cycles, the catalysts maintained the activity.
