Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and first-principles calculations are performed to investigate the different ways in which water reacts with a SnO 2 surfaces and to evaluate the cross interference of humidity on the detection of CO. Two different materials, chosen because of their very different properties, were investigated. The experimental results were interpreted with the help of theoretical modelling of two clean and defective surfaces, namely (110) and (101). The experimental results show, and the theoretical calculations confirm, that water vapor can interfere with the CO detection in different ways depending on the active surface and the concentration of oxygen vacancies. This is related to the different ways in 2 which the water vapor reacts with tin oxide; on the one hand it can reduce the (101) surface, on the other hand it can heal the oxygen vacancies of the defective (110) surface.
The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (γ-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species.
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