Department of Chemistry, The University of Aberdeen, Aberdeen AB24 3UE, UK.
Phys Chem Chem Phys. 2012 Sep 14;14(34):11910-9. doi: 10.1039/c2cp40641a. Epub 2012 Jul 26.
Studies of the modes of adsorption and the associated changes in electronic structures of renewable organic compounds are needed in order to understand the fundamentals behind surface reactions of catalysts for future energies. Using planewave density functional theory (DFT) calculations, the adsorption of ethanol on perfect and O-defected TiO(2) rutile (110) surfaces was examined. On both surfaces the dissociative adsorption mode on five-fold coordinated Ti cations (Ti(4+)(5c)) was found to be more favourable than the molecular adsorption mode. On the stoichiometric surface E(ads) was found to be equal to 0.85 eV for the ethoxide mode and equal to 0.76 eV for the molecular mode. These energies slightly increased when adsorption occurred on the Ti(4+)(5c) closest to the O-defected site. However, both considerably increased when adsorption occurred at the removed bridging surface O; interacting with Ti(3+) cations. In this case the dissociative adsorption becomes strongly favoured (E(ads) = 1.28 eV for molecular adsorption and 2.27 eV for dissociative adsorption). Geometry and electronic structures of adsorbed ethanol were analysed in detail on the stoichiometric surface. Ethanol does not undergo major changes in its structure upon adsorption with its C-O bond rotating nearly freely on the surface. Bonding to surface Ti atoms is a σ type transfer from the O2p of the ethanol-ethoxide species. Both ethanol and ethoxide present potential hole traps on O lone pairs. Charge density and work function analyses also suggest charge transfer from the adsorbate to the surface, in which the dissociative adsorptions show a larger charge transfer than the molecular adsorption mode.
为了理解未来能源中催化剂表面反应背后的基本原理，需要研究可再生有机化合物的吸附模式和相关电子结构变化。使用平面波密度泛函理论（DFT）计算，研究了乙醇在完美和 O 缺陷锐钛矿（110）TiO 2 表面上的吸附。在两种表面上，五配位 Ti 阳离子（Ti(4+)(5c)）上的解离吸附模式比分子吸附模式更有利。在化学计量表面上，对于乙氧基模式，E(ads)为 0.85 eV，对于分子模式，E(ads)为 0.76 eV。当吸附发生在最接近 O 缺陷位置的 Ti(4+)(5c)上时，这些能量略有增加。然而，当吸附发生在去除桥接表面 O 上并与 Ti(3+)阳离子相互作用时，这两种能量都大大增加。在这种情况下，解离吸附变得非常有利（E(ads)为 1.28 eV 用于分子吸附，2.27 eV 用于解离吸附）。在化学计量表面上，详细分析了吸附乙醇的几何形状和电子结构。乙醇在吸附过程中结构没有发生重大变化，其 C-O 键在表面上几乎可以自由旋转。与表面 Ti 原子的键合是乙醇-乙氧基物种的 O2p 向 σ 型的转移。乙醇和乙氧基都在 O 孤对电子上呈现潜在的空穴陷阱。电荷密度和功函数分析也表明电荷从吸附物转移到表面，其中解离吸附比分子吸附模式表现出更大的电荷转移。
