Response to “Comment by Sadykov and Tikhov”

Abstract

In their comment, Sadykov and Tikhov point out that for copper and copper oxide catalysts that have a substantial amount of bulk phase, the defect structure of the solid influences the catalytic properties. In recent studies to elucidate the effect of the oxidation state of copper on its kinetics of carbon monoxide catalytic oxidation, the authors avoided this problem. The authors utilized evaporated copper thin films of a few monolayers thickness (less than 10 ML) deposited on graphite. When the authors oxidized these samples at various oxygen partial pressures or reduced the copper oxide thin films, equilibria of stoichiometry and oxidation states between the surface and the few bulk layers of copper were achieved in minutes at 3000 or at lower temperatures. This was readily verified by X-ray photoelectron and auger electron spectroscopies. Thus, the catalytic effects due to the presence of bulk defects in three-dimensional copper or copper-oxide phases that do not equilibrate readily with the surface composition and structure were totally absent in these studies.