Roles of Chemisorbed Oxygen and Zinc Oxide Islands on Cu(110) Surfaces for Methanol Decomposition

Article abstract of DOI:10.1021/j100190a076

The interaction of methanol with Cu-Zn-O surfaces is studied on a model system produced by depositing zinc oxide islands on Cu(110) surfaces.Various amounts of oxygen are then adsorbed onto the exposed copper part of the surface to form ZnO_x/y ML O/Cu(110) surfaces.The role of O/Cu(110) in methanol decomposition on our model Cu-Zn-O surfaces was discerned by examining the interaction of methanol, adsorbed at 150 K in ultrahigh vacuum, with these ZnO_x/y ML O/Cu(110) surfaces using temperature-programmed desorption (TPD), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES).Methanol reduces the zinc oxide and removes oxygen chemisorbed on copper.The decomposition temperatures of formate and methoxy species formed upon methanol decomposition on the components of oxygen covered Cu(110) and ZnO_x are unaffected by the presence of the other component.However, the amount of formate species decomposed on the ZnO_x component of ZnO_x/O/Cu(110) surfaces is controlled by the amount of chemisorbed oxygen on copper.We show that there are cooperative effects between O/Cu and ZnO which increases the total amount of formate formed; for ZnO_x/0.2 ML O/Cu(110) surfaces, the concentration of surface formate doubles on the three-component system as compared to the sum of the concentration of formate species on the separate components.This produces a change in the relative surface formate to methoxy ratio from 1:9, for the case of 0.2 ML O/Cu(110), to 1:3, for the case of ZnO_x/0.2 ML O/Cu(110) surfaces.