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

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 A, 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.

分子的 O 2 的激活是在催化黄金的氧化反应的最关键的步；然而，这个过程的内在的机制在争论下面留下。在这研究，我们用密度与包含氢的底层的帮助建议一条其他的 O 2 激活小径功能的理论。这被表明共同吸附的包含 H 底层(RH ) 不仅提高 O 2, 的吸附而且把一个氢原子转移到由它的转变导致 O 2 激活到 hydroperoxyl (OOH ) 的邻近的 O 2, 激进的种类。从 16 的H转移的激活障碍选择了 RH 混合物( H 2 O ， CH 3哦， NH 2 CHCOOH ， CH 3 CH=CH 2,( CH 3)2 SiH 2,等等)到共同吸附的 O ，2是比在大多数情况中的 0.50 eV 低的，在温和条件下面经由 OOH 显示 O 2的激活的可行性。形成的 OOH 氧化剂，与 ~ 的增加的 OO 契约长度 1.45 ? ，也通过在端点的氧原子在氧化反应直接参与，或分裂进原子氧和氢氧根(哦) 由穿过 0.24 eV 的一个相当低的精力障碍。把公司氧化用作一根探针，我们发现了 OOH 比激活的 O 2 和原子氧举办优异活动。这研究为 O 2, 的激活揭示一条新小径并且可以提供卓见进 nanosized 黄金的氧化催化作用。