Molecular Oxygen Adsorption Behaviors on the Rutile TiO2(110)-1 x 1 Surface: An in Situ Study with Low-Temperature Scanning Tunneling Microscopy
Molecular Oxygen Adsorption Behaviors on the Rutile TiO2(110)-1 x 1 Surface: An in Situ Study with Low-Temperature Scanning Tunneling Microscopy
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DOI：
10.1021/ja110375n
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发表时间：
2011-02-16
影响因子：
15
通讯作者：
Hou, J. G.
中科院分区：
文献类型：
--
作者：
Tan, Shijing;Ji, Yongfei;Hou, J. G.
氧在还原金红石型TiO_2（110）~（-1）× 1表面模型体系上的吸附行为对于从原子角度理解许多化学过程具有重要意义。利用扫描隧道显微镜（STM）研究了分子氧在TiO_2（110）~（-1）× 1表面的桥键氧空位（BBOV）和羟基（OH）上的吸附.使用原位O-2剂量的方法，我们能够直接验证的确切吸附位点和分子O-2的动力学行为。我们的实验提供了直接的证据，O-2分子可以内在地吸附在BBOV和OH网站。已经确定的是，在低覆盖度的O-2，在BBOV的单吸附分子O-2可以通过一个中间态的驱动STM针尖解离。然而，单吸附在OH分子O-2可以从这样的尖端诱导的效果，这意味着单吸附在OH的O-2是更稳定的比在BBOV。有趣的是，观察到当BBO（V）s完全充满过量的O-2剂量，吸附的O-2分子在BBOV往往是非解离的，即使在更高的偏置电压为2.2 V。这种非解离的行为是最有可能归因于存在两个或更多的O-2分子同时吸附在BBOV具有更稳定的配置比单吸附分子O-2在BBOV。
A knowledge of adsorption behaviors of oxygen on the model system of the reduced rutile TiO2(110)-1 x 1 surface is of great importance for an atomistic understanding of many chemical processes. We present a scanning tunneling microcopy (STM) study on the adsorption of molecular oxygen either at the bridge-bonded oxygen vacancies (BBOV) or at the hydroxyls (OH) on the TiO2(110)-1 x 1 surface. Using an in situ O-2 dosing method, we are able to directly verify the exact adsorption sites and the dynamic behaviors of molecular O-2. Our experiments provide direct evidence that an O-2 molecule can intrinsically adsorb at both the BBOV and the OH sites. It has been identified that, at a low coverage of O-2, the singly adsorbed molecular O-2 at BBOV can be dissociated through an intermediate state as driven by the STM tip. However, singly adsorbed molecular O-2 at OH can survive from such a tip-induced effect, which implies that the singly adsorbed O-2 at OH is more stable than that at BBOV. It is interesting to observe that when the BBO(V)s are fully filled with excess O-2 dosing, the adsorbed O-2 molecules at BBOV tend to be nondissociative even under a higher bias voltage of 2.2 V. Such a nondissociative behavior is most likely attributed to the presence of two or more O-2 molecules simultaneously adsorbed at a BBOV with a more stable configuration than singly adsorbed molecular O-2 at a BBOV.