No abstract

Catalytic combustion has been widely applied to remove the trace combustible pollutants. However, the earthabundant and high-performance nanocatalysts are still the main research focus on promoting catalytic efficiency. Herein, the Cu and Mn mixed oxides supported on TiO 2 nanoparticles with various Cu and Mn molar contents synthesized via the flame spray pyrolysis (FSP) technique are utilized in the catalytic oxidation of lean CO and CH 4 . Initially, the Cu−Mn/TiO 2 nanocatalysts are composed of spherical structures with a diameter of about 20 nm, whose specific surface area is between 60 and 90 m 2 /g. The Cu element is more evenly distributed on the TiO 2 surface than the Mn element, owing to the distinctly different ion radii. Both the copper and manganese cations could incorporate into the TiO 2 lattice, which generates oxygen vacancies and enhances the diffusion of oxygen ions, causing the transformation of the antanse to rutile phase. When the molar content of the Cu−Mn increases to less than 30 mol %, the temperature of its reduction peak keeps decreasing due to the hydrogen spillover effect. Moreover, the catalytic performances of the Cu−Mn/TiO 2 with 12 mol % loading (12CMT) are all optimal during the low-temperature and the high-temperature stages, which are superior to the FSP-made copper manganese or copper titanium oxides. This is attributed to the small crystal particles, highly dispersed active components of CuO x and MnO x , and the higher ratios of Cu 1+ /Cu and Mn 4+ −O ads Lewis acid−base pairs. In addition, the strong interaction between Cu−Mn components and rutile phase support can tremendously promote the activity of catalytic combustion. Under the simulated flue gas, the catalytic properties of 12CMT decreases in comparison with those of CO and CH 4 mixed gas due to the introduction of CO 2 . Ultimately, the Cu−Mn/TiO 2 samples exhibit the outstanding water resistance, thanks to the hydrophobization of the catalyst surface.

As a non-noble-metal catalyst, CuO has great potential in the catalytic combustion of CO and CH 4 . In this work, the influence of loading active copper components onto perovskites and essential operating parameters in flame aerosol synthesis has been experimentally and theoretically investigated to optimize the catalytic efficiency for the complete oxidation of lean CO and CH 4 . Herein, the CuO−SrTiO 3 nanocatalysts are onestep-synthesized by flame spray pyrolysis with varied copper loadings and precursor feeding rates. The sample under the precursor flow rate of 3 mL/min and the CuO loading of 15 mol % demonstrates optimal catalytic performance. It is primarily attributed to the excellent low-temperature reducibility and improved activity of copper species originated by CuO quantum dots and metal−support interaction. Besides, SrTiO 3 perovskite as a support can effectively inhibit the sintering of CuO quantum dots at high temperatures, which is responsible for the excellent sintering and water deactivation resistances.

Perovskites have been recognized as affordable substitutes for noble-metal catalysts for their tunable catalytic activity and thermal stability. Nevertheless, the highly demanding synthesis procedure still hinders the application of perovskites in catalytic combustion. In this work, a series of nanostructured SiTiO3 perovskites with B-site partial substitution by Co, Fe, Mn, Ni, and Cu are synthesized via flame spray pyrolysis in one step. The comprehensive characterizations on textural properties of nanostructured perovskites reveal that the flame-made perovskite nanoparticles all exhibit high crystal purity and large specific surface area (∼40 m2/g). Furthermore, the highest catalytic activity is achieved by SrTi0.5Co0.5O3 due to the formation of favorable oxygen vacancies, outstanding reducibility, and oxygen desorption capability. Additionally, the presence of 10 vol % water vapor during long-term testing indicates remarkable durability and water resistance. Finally, the CO oxidation and CH4 dehydrogenation on SrTiO3 incorporating Co atoms are more thermodynamically and kinetically favorable than those on other doped surfaces.