Flame In Situ Synthesis of Metal-Anchored CuO Nanowires for CO Catalytic Oxidation and Kinetic Analysis

Abstract

Flame in situ synthesis is regarded as a facile technique to fabricate onedimensional (1D) nanomaterials with the advantages of simple operation, shorter duration, and scale production. This work reports the flame synthesis of transition metal (Ce,Fe)anchored CuO nanowires on a copper substrate for CO catalytic oxidation. Thermal compressive stresses encourage the CuO nanowires to grow vertically along the grain boundaries, and the metal oxides are nucleated and embedded along the nanowires due to pyrolysis. We examined the catalytic performance of the as-grown catalysts toward CO oxidation, and the results showed that the CeFe-Cu catalyst exhibits outstanding activity near full conversion at 180 °C. With a reaction rate per unit mass of 1.38 mol g cat −1 s −1 and activation energy of 43.54 kJ mol −1 , the high activity of the CeFe-Cu catalyst benefits from the synergistic effects of Ce-Fe incorporation. Furthermore, the CeFe-Cu catalyst displays stable cycling performance over five runs and excellent stability in isothermal long-term catalysis tests at 140 °C. Kinetic analysis gives the rate equations for CO oxidation over the Ce-Cu, Fe-Cu, and CeFe-Cu catalysts and reveals the influential role of chemisorbed CO and lattice oxygen in the reaction. The catalytic oxidation of CO undergoes two reduction−oxidation steps as corroborated by the Mars Van Krevelen (MVK) model, and oxygen vacancies are crucial to facilitating the deep oxidation of CO, as confirmed by XPS. Meanwhile, combined with in situ Raman analysis, a reasonable mechanism is proposed. This work provides a fast method of designing 1D hybrid nanostructures for the abatement of carbon monoxide from exhaust gas emissions.

Catalytic Combustion Study of Ethanol Over Manganese Oxides with Different Morphologies

“…66 In situ Raman spectra (Figure 4) were also recorded in an air flow by varying the temperature from 323 to 493 K. With the increase in temperature, a slight shift demonstrates the desorption of the latticed oxygen or phase transformation. 67 The maximum offset value from 643 to 634 cm −1 appeared in the Mn 3 O 4 nanoplate that verifies the intense lattice distortion, while the formation of a band around 530 cm −1 can be explained by the desorption of surface lattice oxygen species. 68 The defects and oxygen vacancies lead to the outstanding ability of oxygen migration and an enhanced catalytic performance for ethanol combustion.…”

“…On the other hand, a lower band at 643 cm –1 for the Mn 3 O 4 nanoplate with the broadening of peak width is observed, which might be originated from the generation of the defective structure of the nanoplate material and is favorable to activate the surface adsorption oxygen molecules . In situ Raman spectra (Figure ) were also recorded in an air flow by varying the temperature from 323 to 493 K. With the increase in temperature, a slight shift demonstrates the desorption of the latticed oxygen or phase transformation . The maximum offset value from 643 to 634 cm –1 appeared in the Mn 3 O 4 nanoplate that verifies the intense lattice distortion, while the formation of a band around 530 cm –1 can be explained by the desorption of surface lattice oxygen species .…”

CuO/TiO2/Ti Monolithic Catalysts for Low-Temperature CO Oxidation

“…The lattice oxygen and the surface O v play an important role in this reaction, which has also been confirmed in the literature. 60,61…”

Fabrication of γ-Al2O3 Nanoarrays on Aluminum Foam Assisted by Hydroxide for Monolith Catalysts

“…Metal substrates can be covered by a “washcoat” with in situ growth, resulting in greater adhesion between substrates and overlayer due to chemical linkages. Open-cell metal substrates, for example, have been proposed for the removal of gaseous pollutants, − water treatment, , reforming of methane, supercapacitors, fuel cells, thermal storage, and so on. Furthermore, the coefficient of thermal conductivity of metals such as Al (∼237 W m –1 K –1 ) is hundreds of times greater than that of cordierite, resulting in more uniform temperature distribution and improved heat efficiency when employed on a broad scale.…”

“…As a result, metal foam-based monolithic catalysts will be a viable option. As is well known, hydrothermal or thermal methods are used to prepare open-cell metal substrates for in situ generated washcoat. ,, However, neither hydrothermal nor thermal methods can easily prepare the monolithic catalyst at lower temperatures and offer the probability of scalable production.…”