Nanosized rod-like, wire-like, and tubular α-MnO(2) and flower-like spherical Mn(2)O(3) have been prepared via the hydrothermal method and the CCl(4) solution method, respectively. The physicochemical properties of the materials were characterized using numerous analytical techniques. The catalytic activities of the catalysts were evaluated for toluene oxidation. It is shown that α-MnO(2) nanorods, nanowires, and nanotubes with a surface area of 45-83 m(2)/g were tetragonal in crystal structure, whereas flower-like spherical Mn(2)O(3) with a surface area of 162 m(2)/g was of cubic crystal structure. There were the presence of surface Mn ions in multiple oxidation states (e.g., Mn(3+), Mn(4+), or even Mn(2+)) and the formation of surface oxygen vacancies. The oxygen adspecies concentration and low-temperature reducibility decreased in the order of rod-like α-MnO(2) > tube-like α-MnO(2) > flower-like Mn(2)O(3) > wire-like α-MnO(2), in good agreement with the sequence of the catalytic performance of these samples. The best-performing rod-like α-MnO(2) catalyst could effectively catalyze the total oxidation of toluene at lower temperatures (T(50%) = 210 °C and T(90%) = 225 °C at space velocity = 20,000 mL/(g h)). It is concluded that the excellent catalytic performance of α-MnO(2) nanorods might be associated with the high oxygen adspecies concentration and good low-temperature reducibility. We are sure that such one-dimensional well-defined morphological manganese oxides are promising materials for the catalytic elimination of air pollutants.

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Bimetallic Au–Pd alloy nanoparticles (NPs) dispersed on nanohybrid three-dimensionally ordered macroporous (3DOM) La0.6Sr0.4MnO3 (LSMO) perovskite catalysts were fabricated via the l-lysine-mediated colloidal crystal-templating and reduction routes. The obtained AuPd/3DOM LSMO samples possess a nanovoid-like 3DOM construction with well-dispersed Au–Pd alloy NPs (2.05–2.35 nm in size) on the internal walls of the macropores. The Au–Pd alloy presence favored catalytic activity for methane combustion. The 3DOM LSMO support exhibits three key attributes: (i) a large surface area (32.0–33.8 m2/g) which aids high dispersion of the noble metal NPs on the support surface; (ii) abundant Brønsted acid sites which facilitate reactant adsorption and activation; and (iii) thermal stability. AuPd/3DOM LSMO has been synthesized with beneficial properties, including a richness of adsorbed oxygen species, increased oxidized noble metal species, low-temperature reducibility, and strong noble metal–3DOM LSMO interaction, all contributing to provide enhanced activity and a structure with high thermal and hydrothermal stability. In situ diffuse reflectance infrared Fourier transform spectroscopy studies revealed that including Au in the bimetallic system accelerated the reaction rate and altered the reaction pathway for methane oxidation by enriching the adsorbed oxygen species and decreasing the bonding strength between the reaction intermediates and the Pd atoms.