A Water-Promoted Mechanism of Alcohol Oxidation on a Au(111) Surface: Understanding the Catalytic Behavior of Bulk Gold

To understand the catalytic mechanism of alcohol oxidation with molecular oxygen on bulk metallic gold catalysts, we have systematically studied the oxidative dehydrogenation of methanol on Au(111) using density functional theory. It is found that molecular oxygen can be activated via a hydroperoxyl (OOH) intermediate produced by abstracting a hydrogen atom from co-adsorbed methanol or water. Interestingly, extra water molecules significantly promote the hydrogen-transfer reactions between CH3OH center dot center dot center dot O-2 and H2O center dot center dot center dot O-2 co-adsorbates, lowering the activation barrier of OOH formation from similar to 0.90 to similar to 0.45 eV. The formed OOH intermediate either directly reacts with methanol to produce formaldehyde or dissociates into adsorbed atomic oxygen and hydroxyl. Further calculations demonstrate that the oxidative dehydrogenation of methanol by OOH, atomic oxygen, and hydroxyl is extremely facile with low barriers between 0.06 and 0.30 eV. These results provide an explanation for the activation mechanism of molecular oxygen on bulk gold and reveal a possible pathway for alcohol oxidation with dioxygen.