Hierarchical NiMn2O4/rGO composite nanosheets decorated with Pt for low-temperature formaldehyde oxidation

Abstract

Formaldehyde (HCHO) is a major pollutant affecting indoor air quality. Exposure to HCHO would cause serious health risks to humans, so it is an urgent issue to remove indoor HCHO. Catalytic oxidation is deemed to be the optimal method because of its efficiency and convenience. Herein, a hierarchical nanocomposite of spinel nickel–manganese mixed oxide (NiMn₂O₄) and reduced graphene oxide (rGO) was synthesized by a facile hydrothermal process, and platinum (Pt) nanoparticles were subsequently deposited by an impregnation–chemical reduction procedure. The Pt/NiMn₂O₄/rGO nanocomposite exhibited enhanced HCHO decomposition activity at room temperature, owing to its unique features. The hierarchical structure endows it with abundant pores and a large specific surface area, which favors the dispersion of Pt nanoparticles and contributes to more surface active sites. As revealed by X-ray photoelectron spectroscopy analysis, the interactions between components were also important factors for achieving the excellent catalytic performance, in that electron transfer between the components could promote the activation of surface oxygen species and adsorbed oxygen molecules. In situ diffuse reflectance infrared Fourier transform spectroscopy was performed to explore the oxidation mechanism, and the results showed that the major intermediates in the oxidation process were dioxymethylene and formate species. This study indicates that nanocomposites of rGO and transition metal oxide nanosheets are potential materials for efficient indoor air purification.