Hierarchical Pt/MnO2–Ni(OH)2 Hybrid Nanoflakes with Enhanced Room-Temperature Formaldehyde Oxidation Activity

Nickel foam (NF)-supported Pt/MnNi@NF catalyst was prepared via in situ hydrothermal growth of manganese dioxide–nickel­(II) hydroxide (MnO2–Ni­(OH)2) hierarchical nanosheets and subsequent impregnation–borohydride reduction to deposit well-dispersed platinum (Pt) nanoparticles (NPs). The free-standing composite catalyst exhibited improved performance for room-temperature formaldehyde (HCHO) oxidation due to synergistic effect of Pt, MnNi nanosheets, and the NF substrate, considering the lack of HCHO oxidation activity in the absence of Pt or MnO2–Ni­(OH)2 and low activity of powder-like Pt/MnO2–Ni­(OH)2 in the absence of NF. Surface hydroxyl (OH) groups of MnO2 and Ni­(OH)2 were helpful for the adsorption of HCHO, while Pt NPs facilitated the formation of active oxygen species. Besides, oxygen vacancies on the surface of MnO2 were beneficial for the migration of active oxygen species. The NF not only served as a substrate but also contributed to the formation of thinner nanosheets with larger lateral size and smaller grain size, thus exposing more active sites and improving the homogeneous dispersion of Pt nanoparticles. Therefore, this NF-supported free-standing composite catalyst holds great promise for application in indoor HCHO abatement.