Dehydrogenation of methanol on Cu2O(100) and (111)

Zahra Besharat; Joakim Halldin Stenlid; Markus Soldemo; Kess Marks; Anneli Önsten; Magnus Johnson; Henrik Öström; Jonas Weissenrieder; Tore Brinck; Mats Göthelid

doi:10.1063/1.4989472

Dehydrogenation of methanol on Cu₂O(100) and (111)

J Chem Phys. 2017 Jun 28;146(24):244702. doi: 10.1063/1.4989472.

Affiliations

¹ Material Physics, KTH Royal Institute of Technology, SCI, S-164 40 Kista, Sweden.
² Applied Physical Chemistry, School of Chemical Science and Engineering, KTH Royal Institute of Technology, S-100 44 Stockholm, Sweden.
³ Department of Physics, Stockholm University, S-106 91 Stockholm, Sweden.
⁴ Division of Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology, Stockholm S-100 44, Sweden.

PMID: 28668016
DOI: 10.1063/1.4989472

Abstract

Adsorption and desorption of methanol on the (111) and (100) surfaces of Cu₂O have been studied using high-resolution photoelectron spectroscopy in the temperature range 120-620 K, in combination with density functional theory calculations and sum frequency generation spectroscopy. The bare (100) surface exhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface. Heating transforms methoxy to formaldehyde, but further dehydrogenation is limited by the stability of the surface and the limited access to surface oxygen. The (√3 × √3)R30°-reconstructed (111) surface is based on ordered surface oxygen and copper ions and vacancies, which offers a palette of adsorption and reaction sites. Already at 140 K, a mixed layer of methoxy, formaldehyde, and CH_xO_y is formed. Heating to room temperature leaves OCH and CH_x. Thus both CH-bond breaking and CO-scission are active on this surface at low temperature. The higher ability to dehydrogenate methanol on (111) compared to (100) is explained by the multitude of adsorption sites and, in particular, the availability of surface oxygen.