Interaction of water and methanol with oxygen-modified ZrC(1 0 0) surfaces

The reactivity of oxidized ZrC(1 0 0) surfaces toward H2O and CH3OH adsorption has been investigated using X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. It is found that the reactivity of the ZrC(1 0 0) surface toward H2O adsorption is much enhanced when the surface is covered with an ordered suboxide (ZrO) like layer; H2O does not adsorb on the ZrC(1 0 0) surface but adsorbs dissociatively forming hydroxyl (OH) and atomic O adsorbates on the surface covered with the ZrO-like layer. When the surface is covered with a disordered ZrOx (1<x<2) layer, H2O also adsorbs dissociatively forming hydroxyl adsorbates, but the sticking probability up to 1 L is estimated to be ∼45% of that on the ZrO-like surface. CH3OH is found to adsorb dissociatively forming methoxy (CH3O) adsorbates on both oxidized surfaces while CH3OH adsorbs molecularly on the ZrC(1 0 0) surface. Thus, the dissociation of CH3OH is facilitated on both oxidized surfaces, however, the sticking probabilities of CH3OH on the ZrC(1 0 0) surface and on the oxidized surfaces are found to be comparable.