Catalytic oxidation of formaldehyde (HCHO) is the most efficient way to purify indoor air of HCHO pollutant. This work investigated rare earth La-doped Pt/TiO2 for low concentration HCHO oxidation at room temperature. La-doped Pt/TiO2 had a dramatically promoted catalytic performance for HCHO oxidation. The reasons for the La promotion effect were investigated by N2 adsorption, X-ray diffraction, CO chemisorption, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and high-angle annular dark field scanning TEM. The Pt nanoparticle size was reduced to 1.7 nm from 2.2 nm after modification by La, which led to higher Pt dispersion, more exposed active sites and enhanced metal-support interaction. Thus a superior activity for indoor low concentration HCHO oxidation was obtained. Moreover, the La-doped TiO2 can be wash-coated on a cordierite monolith so that very low amounts of Pt (0.01 wt%) can be used. The catalyst was evaluated in a simulated indoor HCHO elimination environment and displayed high purifying efficiency and stability. It can be potentially used as a commercial catalyst for indoor HCHO elimination.La-doped TiO2 was used to support Pt and the catalyst displayed superior catalytic performance in the removal of low concentration HCHO at room temperature.Download high-res image (100KB)Download full-size image

•Mesoporous SiO2 with different morphologies were synthesized as supports for Ag.•Fibrous KCC-1 SiO2 sphere can provide open pores and easy access high surface.•Ag on KCC-1 has much smaller grain size and higher activity than on other supports.•A linear relationship is revealed between the inherent activity and Ag grain size.•Ag grain size and active metal surface area are the determining factors for its activity.With the objective to prepare better CO oxidation catalysts and explore the inherent factors to determine the activity of supported Ag catalysts, KCC-1, SBA-15 and MCM-41, a series of mesoporous SiO2 with different morphologies, have been synthesized and used as supports for Ag to prepare catalysts (7% Ag/KCC-1, 7% Ag/SBA-15 and 7% Ag/MCM-41) for CO oxidation. It is found that the morphologies of the SiO2 supports influence the dispersion of the supported Ag species, thus resulting in catalysts with different Ag grain sizes and active metallic surface areas, as proved by XRD and H2 adsorption-desorption results. With fibrous KCC-1 silica spheres as the support, the mobilization and aggregation of the Ag particles can be effectively hindered by the open access surface mesopores. Therefore, compared with SBA-15 and MCM-41, Ag nanoparticles with much smaller grain sizes have been achieved, thus resulting in a catalyst with significantly improved activity. Furthermore, a linear relationship has been found between the differential CO oxidation rates and the Ag grain size. Therefore, it is concluded that the active Ag metal surface area is the determining factor for the activity of the silica supported Ag catalysts.Morphologies of the SiO2 supports influence the dispersion of the supported Ag species, thus resulting in catalysts with different Ag sizes and active Ag metallic surface areas, which are the determining factors for the activity of the catalysts. With dendritic KCC-1 SiO2 spheres as the support, the migration and agglomeration of the Ag nanoparticles was effectively impeded by the fibrous surface, thus resulting in a catalyst with superior CO oxidation activity.