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

Converting carbon dioxide (CO) 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 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 both alone and in the presence of HO at 298 K. We find that CO reacts with surface O on Ag to form a chemisorbed species (O = CO). Adding HO and CO then leads to up to four water attaching on O = CO and two water attaching on chemisorbed (b-)CO. On Ag we find a much more favorable mechanism involving the O = CO compared to that involving b-CO on Cu. Each metal surface modifies the gas-catalyst interactions, providing a basis for tuning CO adsorption behavior to facilitate selective product formations.