Dramatic differences in carbon dioxide adsorption and initial steps of reduction between silver and copper

Abstract

Converting carbon dioxide (CO 2 ) into liquid fuels and synthesis gas is a world-wide priority. But there is no experimental information on the initial atomic level events for CO 2 electroreduction on the metal catalysts to provide the basis for developing improved catalysts. Here we combine ambient pressure X-ray photoelectron spectroscopy with quantum mechanics to examine the processes as Ag is exposed to CO 2 both alone and in the presence of H 2 O at 298 K. We find that CO 2 reacts with surface O on Ag to form a chemisorbed species (O = CO 2d- ). Adding H 2 O and CO 2 then leads to up to four water attaching on O = CO 2d- and two water attaching on chemisorbed (b-)CO 2 . On Ag we find a much more favorable mechanism involving the O = CO 2d- compared to that involving b-CO 2 on Cu. Each metal surface modifies the gas-catalyst interactions, providing a basis for tuning CO 2 adsorption behavior to facilitate selective product formations.