Applications of silver nanocatalysts for low-temperature oxidation of carbon monoxide

Transition Metal (Fe2O3, Co3O4 and NiO)-Promoted CuO-Based α-MnO2 Nanowire Catalysts for Low-Temperature CO Oxidation

As a toxic pollutant, carbon monoxide (CO) usually causes harmful effects on human health. Therefore, the thermally catalytic oxidation of CO has received extensive attention in recent years. The CuO-based catalysts have been widely investigated due to their availability. In this study, a series of transition metal oxides (Fe2O3, Co3O4 and NiO) promoted CuO-based catalysts supported on the α-MnO2 nanowire catalysts were prepared by the deposition precipitation method for catalytic CO oxidation reactions. The effects of the loaded transition metal type, the loading amount, and the calcination temperature on the catalytic performances were systematically investigated. Further catalyst characterization showed that the CuO/α-MnO2 catalyst modified with 3 wt% Co3O4 and calcined at 400 °C performed the highest CO catalytic activity (T90 = 75 °C) among the investigated catalysts. It was supposed that the loading of the Co3O4 dopant not only increased the content of oxygen vacancies in the catalyst but also increased the specific surface area and pore volume of the CuO/α-MnO2 nanowire catalyst, which would further enhance the catalytic activity. The CuO/α-MnO2 catalyst modified with 3 wt% NiO and calcined at 400 °C exhibited the highest surface adsorbed oxygen content and the best normalized reaction rate, but the specific surface area limited its activity. Therefore, the appropriate loading of the Co3O4 modifier could greatly enhance the activity of CuO/α-MnO2. This research could provide a reference method for constructing efficient low-temperature CO oxidation catalysts.

One-Pot Method to Synthesize Silver Nanoparticle-Modified Bamboo-Based Carbon Aerogels for Formaldehyde Removal

The present study demonstrated a freeze-drying-carbonization method to synthesize silver nanoparticle-modified bamboo-based carbon aerogels to remove formaldehyde. The bamboo-based carbon aerogel (BCA) has the advantages of controllable pore size and rich oxygen-containing groups, which can provide a good foundation for surface modification. BCA can greatly enhance the purification of formaldehyde by loading silver nanoparticles. The maximum adsorption capacity of 5% Ag/BCA for formaldehyde reached 42 mg/g under 25 ppm formaldehyde concentration, which is 5.25 times more than that of BCA. The relevant data were fitted by the Langmuir model and the pseudo 2nd-order model and good results were obtained, indicating that chemical absorption occurred between the carbonyl of formaldehyde and the hydroxyl of BCA. Therefore, silver nanoparticle-modified bamboo-based carbon aerogels play a positive role in the selective removal of formaldehyde. Silver nanoparticles promoted the activation of oxygen and strengthened the effect of BCA on HCHO adsorption.

Metal oxide/CeO2 nanocomposites derived from Ce-benzene tricarboxylate (Ce-BTC) adsorbing with metal acetylacetonate complexes for catalytic oxidation of carbon monoxide

Herein, a series of metal oxide/CeO₂ (M/CeO₂) nanocomposites derived from Ce-benzene tricarboxylate (Ce-BTC) adsorbing with different metal acetylacetonate complexes were prepared for CO oxidation under four different CO gas atmospheres. It was demonstrated that Cu/CeO₂ exhibited the highest catalytic activity and stability in CO oxidation. Remarkably, both O₂ selectivity and CO selectivity to CO₂ are 100% in most of the investigated conditions. Several analytical tools such as N₂ adsorption-desorption and powder X-ray diffraction, were employed to characterize the prepared catalysts. In addition, the excellent catalytic performance of Cu/CeO₂ in CO oxidation was revealed by H₂ temperature-program reduction experiment, X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The result showed that high oxygen vacancy and high CO adsorption capacity (Cu⁺-CO) caused by the electron exchanges of Cu²⁺/Cu⁺ and Ce³⁺/Ce⁴⁺ pairs (Ce⁴⁺ + Cu⁺ ⇆ Ce³⁺ + Cu²⁺) are two key factors contributing to the high oxidation performance of Cu/CeO₂ catalyst.