Oxygen reduction on silver low-index single-crystal surfaces in alkaline solution:: Rotating ring DiskAg(hkl) studies

The rotating ring disk method is applied to investigate the oxygen reduction reaction on Ag single-crystal peratures, the oxygen reduction surfaces in alkaline solution over the temperature range 293-333 K. At all tern reaction proceeds through the 4e(-) reaction pathway with a very small (approximate to 0.5-2%) peroxide formation. At the same temperature and overpotentials, the kinetics of the ORR always increases in the order (100) <= (111) < (110), indicating that the reaction is structure-sensitive. We present an interpretation of the structure sensitivity based on the supposition that it arises from (i) a potential-dependent adsorption of spectator hydroxyl ions and (ii) variations in activation energies, which are determined by the O-2 adsorption on Ag single-crystal surfaces covered by adsorbed oxygenated species.