A METHANOL–WATER COMPLEX STABILIZED ON A Zn(0001) SURFACE

Abstract

Coadsorption of water and methanol on a clean Zn(0001) surface has been investigated by employing X-ray photoelectron spectroscopy after exposing the surface at 80 K to the binary vapor from water–methanol liquid mixtures of varying compositions and subsequently warming the surface up to the room temperature. When the surface was exposed to the vapor from a mixture with water molefraction, xw, of 0.5, the proton abstraction and the C–O bond cleavage in methanol leading to methoxy (CH3O) and the hydrocarbon ( CH x) species respectively, occurs at a much higher temperature of 180 K, compared to 120 K in the case of pure methanol adsorption. For water-rich mixtures (xw = 0.7 and 0.9) molecular methanol is stabilized on the surface up to 200 K, beyond which water itself desorbs. For xw = 0.7, virtually no dissociation is observed up to 200 K. The increased stability of molecular methanol on the Zn(0001) surface is attributed to the surface-mediated hydrogen bonds that stabilize a water–methanol complex.