Effect of Surface Deposited Pt on the Photoactivity of TiO2
Effect of Surface Deposited Pt on the Photoactivity of TiO2
复制标题
DOI：
10.1021/jp301862m
复制
发表时间：
2012-05-10
影响因子：
3.7
通讯作者：
Musgrave, Charles B.
中科院分区：
文献类型：
--
作者：
Muhich, Christopher L.;Zhou, Yun;Musgrave, Charles B.
使用密度泛函理论研究了沉积的 Pt 簇和吸附的 O-2 在锐钛矿 TiO2 (101) 表面光活性中的作用。仅当有多余的负电荷可形成 O-Ti 键时，O-2 才会吸附到 TiO2 表面，这可由光激发电子或表面下氧空位提供，在这种情况下，吸附能分别为 -0.94 和 -2.52 eV。当 O-2 吸附在地下缺陷附近时，它会清除额外的电子密度并产生一个可以湮灭激发电子的空穴。在水溶液中，O-2 与 TiO2 表面的相互作用很少，因为水优先吸附在表面。 TiO2 上的 Pt 簇显着增强了 O-2 吸附，提供了许多吸附位点，吸附能高达 -1.69 eV，强于 Pt 簇上 H2O 的 -0.52 eV 吸附能。因此，相对于未掺杂的 TiO2，Pt 增加了 O-2 的电子清除速率，从而增强了光催化性能。 Pt 态完全桥接带隙并充当电子-空穴复合中心，这对 TiO2 的光活性有害。随着 Pt 负载量的增加，TiO2 光活性的最初上升和随后的下降是由于 O-2 吸附增加和电子空穴复合增加导致的电子清除增强之间的竞争造成的。
The roles of deposited Pt clusters and adsorbed O-2 in the photoactivity of anatase TiO2 (101) surfaces have been studied using density functional theory. O-2 only adsorbs to TiO2 surfaces when excess negative charge is available to form O-Ti bonds, which can be provided by a photoexcited electron or subsurface oxygen vacancy, in which cases the adsorption energies are -0.94 and -2.52 eV, respectively. When O-2 adsorbs near a subsurface defect, it scavenges extra electron density and creates a hole that can annihilate excited electrons. In aqueous solutions, O-2 interactions with the TiO2 surface are rare because water preferentially adsorbs at the surface. Pt clusters on TiO2 significantly enhance O-2 adsorption providing many adsorption sites with adsorption energies up to -1.69 eV, stronger than the -0.52 eV adsorption energy of H2O on the Pt cluster. Consequently, Pt increases the rate of electron scavenging by O-2 relative to that of undoped TiO2 leading to enhanced photocatalytic performance. Pt states completely bridge the band gap and act as electron-hole recombination centers, which are deleterious to the photoactivity of TiO2. The initial rise and subsequent fall in TiO2's photoactivity with Pt loading results from the competition between enhanced electron scavenging due to increased O-2 adsorption and increased electron-hole recombination.