Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
J Am Chem Soc. 2010 Mar 10;132(9):3177-86. doi: 10.1021/ja910146g.
High-resolution photoemission and density functional calculations on realistic slab surface models were used to study the interaction and subsequent dissociation of O(2) with Au nanoparticles supported on TiC(001). The photoemission results indicate that at 150 K O(2) adsorbs molecularly on the supported gold nanoparticles, and upon heating to temperatures above 200 K the O(2) --> 2O reaction takes place with migration of atomic oxygen to the TiC(001) substrate. The addition of Au to TiC(001) substantially enhances the rate of O(2) dissociation at room temperature. The reactivity of Au nanoparticles supported on TiC(001) toward O(2) dissociation is much larger than that of similar nanoparticles supported either on TiO(2)(110) or MgO(001) surfaces, where the cleavage of O-O bonds is very difficult. Density functional calculations carried out on large supercells show that the contact of Au with TiC(001) is essential for charge polarization and an enhancement in the chemical activity of Au. Small two-dimensional particles which expose Au atoms in contact with TiC(001) are the most reactive. While O(2) prefers binding to Au sites, the O atoms interact more strongly with the TiC(001) surface. The oxygen species active during the low-temperature (<200 K) oxidation of carbon monoxide on Au/TiC(001) is chemisorbed O(2). Once atomic O binds to TiC(001), the chemisorption bond is so strong that temperatures well above 400 K are necessary to remove the O adatoms from the TiC(001) substrate by direct reaction with CO. The high reactivity of Au/TiC(001) toward O(2) at low-temperature opens the route for the transformation of alcohols and amines on the supported Au nanoparticles.
采用高分辨率光电子能谱和密度泛函计算对真实的表面模型进行了研究，以研究 O(2)与负载在 TiC(001)上的 Au 纳米粒子的相互作用和随后的解离。光电子能谱结果表明，在 150 K 时，O(2)分子吸附在负载的金纳米粒子上，当加热到 200 K 以上时，O(2)发生-->2O 反应，原子氧迁移到 TiC(001)衬底。在 TiC(001)上添加 Au 可显著提高室温下 O(2)的解离速率。负载在 TiC(001)上的 Au 纳米粒子对 O(2)解离的反应性远大于负载在 TiO(2)(110)或 MgO(001)表面上的类似纳米粒子，在这些表面上，O-O 键的断裂非常困难。在大超晶胞上进行的密度泛函计算表明，Au 与 TiC(001)的接触对于电荷极化和 Au 的化学活性增强至关重要。暴露与 TiC(001)接触的 Au 原子的二维小颗粒是最具反应性的。虽然 O(2)优先与 Au 位结合，但 O 原子与 TiC(001)表面的相互作用更强。在 Au/TiC(001)上低温 (<200 K) 氧化一氧化碳期间活性的氧物种是化学吸附的 O(2)。一旦原子 O 与 TiC(001)结合，化学吸附键就非常强，以至于需要 400 K 以上的温度才能通过与 CO 的直接反应将 O adatoms 从 TiC(001)衬底中去除。Au/TiC(001)在低温下对 O(2)的高反应性为负载在 Au 纳米粒子上的醇和胺的转化开辟了道路。
