Department of Chemical and Biomolecular Engineering, 182 Fitzpatrick Hall, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Langmuir. 2011 Jul 5;27(13):8177-86. doi: 10.1021/la2012028. Epub 2011 Jun 1.
We report a first-principles, periodic supercell analysis of oxygen adsorption, diffusion, and dissociation at the kinked Pt(321) surface. Binding energies and binding site preferences of isolated oxygen atoms and molecules have been determined, and we show that both atomic and molecular oxygen prefer binding in bridge sites involving coordinatively unsaturated kink Pt atoms. Binding energies of atomic and molecular oxygen in different sites correlate well with the average metallic Pt coordination number of Pt atoms forming each site, although differences exist between adsorbates in symmetrically similar sites due to the inherent chirality of the surface. Atomic O in the strongest binding bridge sites experiences relatively small energy barriers for diffusion to neighboring sites compared to O on Pt(111). However, due to the structure of the surface, O diffusion is only rapid between different sites around the kink Pt atom, whereas the effective long-range tracer diffusion, as determined from a simple course-grain model, is shown to be anisotropic and slower than on the Pt(111) surface. Four dissociation pathways for O(2) at low coverage are also reported and found to be in agreement with experimental observations of facile dissociation, even at low temperature.
我们报告了在 Pt(321)扭折表面上氧吸附、扩散和离解的第一性原理、周期性超晶胞分析。确定了孤立氧原子和分子的结合能和结合位点偏好性，并且我们表明，原子氧和分子氧都更喜欢涉及配位不饱和扭折 Pt 原子的桥位结合。不同位置的原子氧和分子氧的结合能与形成每个位置的 Pt 原子的平均金属 Pt 配位数很好地相关，尽管由于表面的固有手性，对称相似位置的吸附物之间存在差异。与 Pt(111)相比，在最强结合桥位的原子 O 经历扩散到相邻位置的相对较小的能量势垒。然而，由于表面的结构，O 扩散仅在扭折 Pt 原子周围的不同位置之间迅速发生，而从简单的粗粒模型确定的有效长程示踪剂扩散则表现出各向异性并且比 Pt(111)表面慢。还报告了在低覆盖度下 O(2)的四种离解途径，并且发现它们与实验观察到的容易离解一致，即使在低温下也是如此。
