Methanol adsorption on magnesium oxide surface with defects: a DFT study

Ethanol adsorption on MgO surface with and without defects from a theoretical point of view

“…Previous works of methanol adsorption on MgO have shown similar results, these bonds having $1.7 and $2.6 Å distances, respectively [18] In this non-dissociative adsorption the ethanol O a AH bond undergoes a small (0.05 Å) stretching from the value for the isolated ethanol, while the CAO a bond undergoes a very slight shortening (0.01 Å). On the other hand, when ethanol is adsorbed on defective edge and corner sites the dissociative adsorption takes place without activation energies.…”

“…A similar trend was obtained in the past for methanol adsorbed on different surface sites of MgO [18]. In order to make a more quantitative comparison between these two molecules with respect to the substrate basicity, in Table 3 are reported the variations of E ads as a function of the coordination number of ions in the adsorption site and expressed relative to the non-dissociative case.…”

“…Moreover, the reactivity of the adsorption sites follows the order: terrace < edge < corner. In particular, the capacity to produce the proton abstraction is, in general, associated with the ion coordination number L, the ions with lower coordination numbers (L = 3) being more reactive than those with higher ones (L = 5) [18][19][20][21]. The greater reactivity of defective MgO has also been theoretically studied in the adsorption of CO [22], NO x [23] and H 2 O [24] on this material.…”

“…In the second mechanism, due to the interaction with surface Mg and O ions the ethanol molecule undergoes the simultaneous abstraction of two H atoms, one a-hydrogen atom of ethanol and another hydrogen atom from the OH group, respectively. On the other hand, theoretical studies of protonated molecules, such as methanol [18,19], isocianic acid [20] and water [21] adsorbed on the MgO (1 0 0) surface with and without defects have revealed that these molecules do not dissociate on perfect sites (terrace sites). Moreover, the reactivity of the adsorption sites follows the order: terrace < edge < corner.…”

Adsorption of Methanol on the MgO(100) Surface: An Infrared Study at Room Temperature

“…Recent theoretical investigations of methanol on MgO support these assignments. 7,16,17 Under typical ultrahigh vacuum (UHV) conditions at both cryogenic temperatures [7][8][9][10][11][12] and room temperature, 11,12 methanol adsorption has also been studied on thin films of MgO(100) by exposing the substrate to a known pressure or coverage of methanol and then reestablishing UHV before examining the surface. For this reason, only the cryogenic studies showed any type of physisorption between the methanol and the MgO(100) surface with methanol wetting the surface and growth occurring in layers, that is, the methanol monolayer is saturated before multilayer formation begins.…”