Three-dimensionally ordered macroporous La0.6Sr0.4MnO3 with high surface areas: Active catalysts for the combustion of methane

Three-dimensionally ordered macroporous rhombohedral La0.6Sr0.4MnO3 (3DOM LSMO) with nanovoids was prepared using polymethyl methacrylate (PMMA) microspheres as a hard template and dimethoxytetraethylene glycol (DMOTEG), ethylene glycol, polyethylene glycol (PEG400), l-lysine, or triblock copolymer (Pluronic P123) as a surfactant. Physicochemical properties of the materials were characterized by a number of analytical techniques, and their catalytic activities for the combustion of methane were evaluated. It is shown that the morphology of the sample depended strongly on the nature of the surfactant added during the fabrication process. The macropore sizes and surface areas of the 3DOM LSMO materials were 165–214 nm and 32–40 m2/g, respectively. It is found that addition of appropriate amounts of DMOTEG and PEG400 was beneficial for the generation of high-quality 3DOM-structured La0.6Sr0.4MnO3 (denoted as LSMO-DP1, LSMO-DP3, LSMO-DP5, derived with a DMOTEG /PEG400 ratio of 0.2, 0.6, and 1.0, respectively). The LSMO-DP3 catalyst derived with 3.0 mL of DMOTEG and 5.0 mL of PEG400 possessed the highest oxygen species concentration and surface area and best low-temperature reducibility, and hence exhibited a good catalytic activity (T10% = 437 °C, T50% = 566 °C, and T90% = 661 °C at GHSV = 30,000 mL/(g h)) for methane combustion. The apparent activation energies of the 3DOM LSMO samples were estimated to be 56.5–75.2 kJ/mol, with the LSMO-DP3 sample showing the lowest apparent activation energy (56.6 kJ/mol).