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Nano Research

Article Title

Hydrogenation of molecular oxygen to hydroperoxyl: An alternative pathway for O2 activation on nanogold catalysts

Keywords

O2 activation, gold cluster, adsorption, dissociation, hydroperoxyl

Abstract

Activation of molecular O2 is the most critical step in gold-catalyzed oxidation reactions; however, the underlying mechanisms of this process remain under debate. In this study, we propose an alternative O2 activation pathway with the assistance of hydrogen-containing substrates using density functional theory. It is demonstrated that the co-adsorbed H-containing substrates (R–H) not only enhance the adsorption of O2, but also transfer a hydrogen atom to the adjacent O2, leading to O2 activation by its transformation to a hydroperoxyl (OOH) radical species. The activation barriers of the H-transfer from 16 selected R–H compounds (H2O, CH3OH, NH2CHCOOH, CH3CH=CH2, (CH3)2SiH2, etc.) to the co-adsorbed O2 are lower than 0.50 eV in most cases, indicating the feasibility of the activation of O2 via OOH under mild conditions. The formed OOH oxidant, with an increased O–O bond length of ~1.45 Å, either participates directly in oxidation reactions through the end-on oxygen atom, or dissociates into atomic oxygen and hydroxyl (OH) by crossing a fairly low energy barrier of 0.24 eV. Using CO oxidation as a probe, we have found that OOH has superior activity than activated O2 and atomic oxygen. This study reveals a new pathway for the activation of O2, and may provide insight into the oxidation catalysis of nanosized gold.

Graphical Abstract

Publisher

Tsinghua University Press

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