La0.5Sr0.5MnO3 single-crystal cubes and nanoparticles were synthesized by hydrothermal and citrate routes, respectively. Their catalytic properties for low-temperature CO oxidation and high-temperature CH4 combustion were evaluated, and the effects of crystal structure and morphology on the catalytic properties of the catalysts were investigated. The activity (220 degrees C of the complete oxidation of CO over the single cubes was lower than that (190 degrees C over the nanoparticles. After running at 600 degrees C for 48 h under the reaction conditions, the surface area of the nanoparticles decreased significantly, but the cubes nearly maintained their surface area. For CH4 combustion, the La0.5Sr0.5MnO3 cubes showed a higher activity (T-10 = 360 degrees C, T-10: the temperature at 10% conversion of CH4) than the nanoparticles (T-10 = 440 degrees C. The different activities were attributed to their different crystal structures and morphologies. (c) 2007 Elsevier Inc. All rights reserved.