The R-, β-, γ-, and δ-MnO 2 nanorods were synthesized by the hydrothermal method. Their catalytic properties for CO oxidation were evaluated, and the effects of phase structures on the activities of the MnO 2 nanorods were investigated. The activities of the catalysts decreased in the order of R-≈ δ-> γ-> β-MnO 2 . The mechanism of CO oxidation over the MnO 2 nanorods was suggested as follows. The adsorbed CO was oxidized by the lattice oxygen, and the MnO 2 nanorods were partly reduced to Mn 2 O 3 and Mn 3 O 4 . Then, Mn 2 O 3 and Mn 3 O 4 were oxidized to MnO 2 by gaseous oxygen. CO chemisorption, the Mn-O bond strength of the MnO 2 , and the transformation of intermediate oxides Mn 2 O 3 and Mn 3 O 4 into MnO 2 can significantly influence the activity of the MnO 2 nanorods. The activity for CO oxidation was mainly predominated by the crystal phase and channel structure of the MnO 2 nanorods.
La 0.5 Sr 0.5 MnO 3 cube and nanoparticle catalysts were synthesized by the hydrothermal and coprecipitation method, respectively. The catalytic performances for CO and CH 4 oxidation were evaluated, and the effect of Jahn-Teller distortion on the catalytic performance was elucidated. La 0.5 Sr 0.5 MnO 3 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 CH 4 oxidation activity was similar to the trend observed for CO oxidation activity. The catalytic mechanism of CO oxidation over La 0.5 Sr 0.5 MnO 3 cubes is proposed that the adsorbed CO was oxidized by the lattice oxygen. Then, the chemisorbed oxygen over La 0.5 Sr 0.5 MnO 3 cubes was transformed into the lattice oxygen by MnO 6 octahedra to reinforce the consumed lattice oxygen. The catalytic performances of La 0.5 Sr 0.5 MnO 3 cubes and nanoparticles were mainly predominated by Jahn-Teller distortion of the catalysts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.