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Hierarchically meso-macroporous γ-Al2O3 hollow microspheres were synthesized at 180 °C for 40 min for the first time by a microwave-assisted hydrothermal (MAH) followed by calcination at 600 °C for 2 h route, using KAl(SO4)2 and urea as raw materials. The results show that the obtained γ-Al2O3 hollow microspheres are about 0.8-1.2 μm in diameter with a shell thickness of approximately 200 nm and the high surface area of 242 m²/g. The prepared γ-Al2O3 hollow microspheres also exhibit an enhanced adsorption performance for Cu2+ in solution than those prepared by hydrothermal (HT) method and commercial γ-Al2O3. [ABSTRACT FROM AUTHOR]

Pt/honeycomb ceramic (Pt/HC) catalysts with ultra-low Pt content (0.005-0.055 wt%) were for the first time prepared by an impregnation of honeycomb ceramics with Pt precursor and NaBH4-reduction combined method. The microstructures, morphologies and textural properties of the resulting samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The obtained Pt/HC catalysts were used for catalytic oxidative decomposition of formaldehyde (HCHO) at room temperature. It was found that the as-prepared Pt/HC catalysts can efficiently decompose HCHO in air into CO2 and H2O at room temperature. The catalytic activity of the Pt/HC catalysts increases with increasing the Pt loading in the range of 0.005-0.013 wt%, and the further increase of the Pt loading does not obviously improve catalytic activity. From the viewpoint of cost and catalytic performance, 0.013 wt% Pt loading is the optimal Pt loading amount, and the Pt/HC catalyst with 0.013 wt% Pt loading also exhibited good catalytic stability. Considering practical applications, this work will provide new insights into the low-cost and large-scale fabrication of advanced catalytic materials for indoor air purification. [ABSTRACT FROM AUTHOR]

Room temperature catalytic oxidation by noble metals is considered to be the most promising strategy for the removal of HCHO, which is one of the major indoor air pollutants. Hierarchically macro-mesoporous structured Pt/γ-Al2O3 hollow spheres with open and accessible pores were synthesized and used for catalytic oxidative decomposition of HCHO at room temperature. The prepared composite hollow spheres showed higher catalytic activity than the conventional nanoparticle supports, which is mainly due to their hierarchical macro-mesoporous structure facilitating diffusion of reactants and products, and the high dispersion of accessible catalytic Pt nanoparticles. This work may contribute to the development of hierarchically structured materials and high-performance catalysts for indoor air purification and related catalytic processes. [ABSTRACT FROM AUTHOR]

Pt/TiO2 catalysts with various Pt loadings (0.05-2 wt %) were prepared by a combined NaOH-assisted impregnation of titania with Pt precursor and NaBH4-reduction. The thermal catalytic activity was evaluated toward catalytic decomposition of formaldehyde (HCHO) vapor in the presence of toluene under ambient conditions. HCHO could be selectively oxidized into CO2 and H2O over Pt/TiO2 catalysts and toluene had no change. Pt/TiO2 catalysts prepared with the assistance of NaOH showed higher HCHO oxidation activity than those without NaOH due to the introduction of additional surface hydroxyl groups, the enhanced adsorption capacity toward HCHO, and larger mesopores and macropores facilitating diffusion and transport of reactants and products. The as-prepared Pt/TiO2 catalysts with an optimal Pt loading of 1 wt % exhibited high catalytic stability. Considering the versatile combination of noble-metal nanoparticles and supports, this work will provide new insights to the design of high-performance catalysts for indoor air purification. [ABSTRACT FROM AUTHOR]