Three-Dimensional Ordered Mesoporous MnO2-Supported Ag Nanoparticles for Catalytic Removal of Formaldehyde.

Three-dimensional (3D) ordered mesoporous Ag/MnO2 catalyst was prepared by impregnation method based on 3D-MnO2 and used for catalytic oxidation of HCHO. Ag nanoparticles are uniformly distributed on the polycrystalline wall of 3D-MnO2. The addition of Ag does not change the 3D ordered mesoporous structure of the Ag/MnO2, but does reduce the pore size and surface area. Ag nanoparticles provide sufficient active site for the oxidation reaction of HCHO, and Ag (111) crystal facets in the Ag/MnO2 are active faces. The 8.9% Ag/MnO2 catalyst shows a higher normalized rate (10.1 nmol·s(-1)·m(-2) at 110 °C) and TOF (0.007 s(-1) at 110 °C) under 1300 ppm of HCHO and 150 000 h(-1) of GHSV, and its apparent activation energy of the reaction is the lowest (39.1 kJ/mol). More Ag active sites, higher low-temperature reducibility, more abundant surface lattice oxygen species, oxygen vacancies, and lattice defects generated from interaction Ag with MnO2 are responsible for the excellent catalytic performance of HCHO oxidation on the 8.9% Ag/MnO2 catalyst. The 8.9% Ag/MnO2 catalyst remained highly active and stable under space velocity increasing from 60 000 to 150 000 h(-1), under initial HCHO concentration increasing from 500 to 1300 ppm, and under the presence of humidity, respectively.