CO 2 adsorption on oxygen-modified Ni(111)

Abstract

Adsorption of CO 2 on Ni(111) oxidised at 300 K has been studied using TPD, XPS and UPS. CO 2 does not adsorb on either clean Ni(111) or on the Ni(111)-p(2 × 2)O overlayer at 300 K. However, it does interact with two distinct binding sites on Ni(111) NiO(111) . The O(1s) and C(1s) XP spectra and the He II UP spectra indicate the formation of CO 3 δ− on the surface of NiO and the CO 3 2− and the CO 3 − species are suggested to be associated with anion vacancies and O −, respectively. The CO 3 − species decomposes during decomposition of the oxide, evolving CO 2 and CO; the latter process may involve dissociation of a CO 2 − intermediate to CO (ads) + O (ads). This occurs on the NiO island sites which are stable up to 690 K. The saturation CO 2 coverage is 0.14 ML with respect to the atomic density of Ni(111).