Low-temperature dissociation of CO₂ molecules on vicinal Cu surfaces

The reaction of carbon dioxide on the vicinal Cu surfaces at low temperatures was investigated by infrared reflection absorption spectroscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy, and quadrupole mass spectrometry. Dissociation of CO₂ molecules into CO on the Cu(997) and Cu(977) surfaces was observed at temperatures between 80 K and 90 K, whereas it did not occur on Cu(111) under a similar condition. CO and physisorbed CO₂ were the main adsorbates during the reaction. In contrast, the amount of atomic oxygen on the surface was small. The dissociation of CO₂ was promoted by the small amount of oxygen produced by the CO₂ dissociation on the Cu surfaces. This leads to the induction period in the CO₂ reaction; the initial reaction rate on the clean Cu surfaces was low, and the coadsorbed oxygen enhanced the dissociation reactivity of CO₂. Mass analysis of desorption species during the reaction revealed that the observed CO formation on the vicinal Cu surface is mainly caused by an oxygen-exchange reaction with residual CO in an ultra-high vacuum chamber.