NiCo-LDH@MnO2 nanocages as advanced catalysts for efficient formaldehyde elimination

Formaldehyde (HCHO) is a harmful gas of volatile organic compounds (VOCs) and its removal is essential to protect human health. Low-temperature elimination of HCHO by non-noble catalysts is one of the most crucial research topics nowadays. Herein, ultrathin MnO 2 nanosheets grown on Ni-Co layered double hydroxide nanocages (NiCo-LDH@MnO 2 ) were fabricated via a hydrothermal method and subsequently used to eliminate HCHO at low temperature. The NiCo-LDH@MnO 2 -1 catalysts (mass ratio of NiCo-LDH to KMnO 4 of 1:1) performed excellent catalytic activity towards HCHO (100 ppm) at 80 °C. After the fifth cycles, the NiCo-LDH@MnO 2 -1 exhibited excellent stable activity towards the oxidation of HCHO. According to the physicochemical characterization analysis, the enhanced catalytic activity over NiCo-LDH@MnO 2 is attributed to the unique hollow nanocage structure, suitable composition , as well as the synergistic influence of MnO 2 and NiCo-LDH. The results of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) presented that the abundant active species (e.g., O 2 − , O − and –OH) can contribute to the adsorption of HCHO on the surface of NiCo-LDH@MnO 2 and promote to oxidize HCHO into the DOM, formate, and carbonate species. Furthermore, NiCo-LDH@MnO 2 displayed good durability for low concentration HCHO (∼9 ppm) at room temperature under 12 h, indicating that the NiCo-LDH@MnO 2 is competitive and inexpensive efficient catalysts for the applications of indoor HCHO purification.