Methanol adsorption on Cu(110) and the angular distribution of the reaction products

Abstract

Integral and angle resolved thermal desorption spectroscopies were used to study methanol adsorption and oxidation on clean and oxygen covered Cu(110) surfaces. Special emphasis was put on the Cu-CuO stripe phase, which forms when the Cu(110) surface is covered with 0.25 ML of oxygen. In the temperature regime between 200 and 300 K associative desorption of methanol and water takes place, showing a normal desorption character with peaks shifting to lower temperature with increasing coverage and with a nearly cosine angular desorption distribution. In the temperature range of about 350 K formaldehyde, hydrogen, and again methanol desorb nearly concomitantly in the form of a very narrow peak (full width at half maximum=10 K), with peaks shifting to higher temperature with increasing methanol coverage. The angular distribution of these peaks is strongly forward focused, indicating activation barriers being involved. In the case of the Cu-CuO stripe phase the angular distribution of the desorption products is clearly different in the [110] and [001] azimuthal directions, demonstrating the influence of the border lines between the copper and the copper oxide stripes on the desorption process.