Three-Dimensionally Ordered Macroporous La0.6Sr0.4MnO3 Supported Ag Nanoparticles for the Combustion of Methane

A series of Ag nanoparticles (NPs) supported on three-dimensionally ordered macroporous (3DOM) La 0.6 Sr 0.4 MnO 3 ( y Ag/3DOM La 0.6 Sr 0.4 MnO 3; y = 0, 1.57, 3.63, and 5.71 wt %) were successfully prepared with high surface areas (38.2–42.7 m 2 /g) by a facile novel reduction method using poly methacrylate colloidal crystal as template in a dimethoxytetraethylene glycol (DMOTEG) solution. Physicochemical properties of these materials were characterized by means of numerous techniques, and their catalytic activities were evaluated for the combustion of methane. It is shown that the y Ag/3DOM La 0.6 Sr 0.4 MnO 3 materials possessed unique nanovoid-like 3DOM architectures, and the Ag NPs were well dispersed on the inner walls of macropores. Among the La 1– x Sr x MnO 3 ( x = 0.2, 0.4, 0.6, 0.8) and y Ag/3DOM La 0.6 Sr 0.4 MnO 3 ( y = 0, 1.57, 3.63, and 5.71 wt %) samples, 3.63 wt % Ag/3DOM La 0.6 Sr 0.4 MnO 3 performed the best, giving T 10%, T 50%, and T 90% (temperatures corresponding to methane conversion =10, 50, and 90%) of 361, 454, and 524 °C, respectively, and the highest turnover frequency (TOF Ag ) value of 1.86 × 10 –5 (mol/mol Ag s) at 300 °C. The apparent activation energies (39.1–37.5 kJ/mol) of the y Ag/3DOM La 0.6 Sr 0.4 MnO 3 samples were much lower than that (91.4 kJ/mol) of the bulk La 0.6 Sr 0.4 MnO 3 sample. The effects of water vapor and sulfur dioxide on the catalytic activity of the 3.63 wt % Ag/3DOM La 0.6 Sr 0.4 MnO 3 sample were also examined. It is concluded that its super catalytic activity was associated with its high oxygen adspecies concentration, good low-temperature reducibility, large surface area, and strong interaction between Ag and La 0.6 Sr 0.4 MnO 3 as well as the unique nanovoid-walled 3DOM structure.