Effect of Jahn−Teller Distortion in La_0.5Sr_0.5MnO₃ Cubes and Nanoparticles on the Catalytic Oxidation of CO and CH₄

Abstract

La0.5Sr0.5MnO3 cube and nanoparticle catalysts were synthesized by the hydrothermal and coprecipitation method, respectively. The catalytic performances for CO and CH4 oxidation were evaluated, and the effect of Jahn−Teller distortion on the catalytic performance was elucidated. La0.5Sr0.5MnO3 nanoparticle catalyst showed a higher activity than the cube catalyst for CO oxidation at a lower temperature. While the catalytic activity of the cubes significantly increased at higher temperature, the complete conversion temperatures for CO were both the same at 210 °C. The trend for CH4 oxidation activity was similar to the trend observed for CO oxidation activity. The catalytic mechanism of CO oxidation over La0.5Sr0.5MnO3 cubes is proposed that the adsorbed CO was oxidized by the lattice oxygen. Then, the chemisorbed oxygen over La0.5Sr0.5MnO3 cubes was transformed into the lattice oxygen by MnO6 octahedra to reinforce the consumed lattice oxygen. The catalytic performances of La0.5Sr0.5MnO3 cubes and nanoparticles were mainly predominated by Jahn−Teller distortion of the catalysts.