SSIMS study of CO 2 adsorption and reactions on clean and oxygen covered Ni(110)

Abstract

Adsorption and reaction of CO2 on transition metal surfaces has received increased interest in recent years. Studies on the system Ni(110)-CO2 gave evidence for the formation of an anionic bent CO−2 prior to dissociation on clean Ni(110) favouring a chemisorption position on top of Ni, whereas oxygen preadsorption stabilizes linearly adsorbed CO2 before the reaction occurs, most probably yielding a carbonate species. We present SSIMS studies on the identical systems clearly proving the formation of CO−3 at a surface temperature above 150 and below 400 K on the Ni(110) surface, requiring more than a threshold coverage with preadsorbed oxygen. On the clean Ni(110) surface, SSIMS yields evidence for the sequence: physisorbed CO2 → chemisorbed bent CO2 → dissociation into COad + Oad → desorption of CO with increasing surface temperature; and hints for an oxygen-down position of the chemisorbed bent CO−2 species can be discussed.