The selective oxidation of ethanol on supported Pd is catalytically promoted by the presence of hydroxide species on the Pd surface as well as in solution. These hydroxide intermediates act as Bronsted bases which readily abstract protons from the hydroxyl groups of adsorbed or solution-phase alcohols. The C-1-H bond of the resulting alkoxide is subsequently activated on the metal surface via hydride elimination to form acetaldehyde. Surface and solution-phase hydroxide intermediates can also readily react with the acetaldehyde via nucleophilic addition to form a germinal did l intermediate, which subsequently undergoes a second C-1-H bond activation on Pd to form acetic acid. The role of O-2 is to remove the electrons produced in the oxidation reaction via the oxygen reduction reaction over Pd. The reduction reaction also regenerates the hydroxide intermediates and removes adsorbed hydrogen that is produced during the oxidation. (C) 2012 Elsevier Inc. All rights reserved.