Effect of vacancy on adsorption/dissociation and diffusion of H2S on Fe(1 0 0) surfaces: A density functional theory study
| Autor: | Xiangli Wen, Weiyu Song, Pengpeng Bai, Teng Fang, Zongying Han, Bingwei Luo, Shuqi Zheng |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
General Physics and Astronomy 02 engineering and technology Surfaces and Interfaces General Chemistry Activation energy 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Bond-dissociation energy Dissociation (chemistry) 0104 chemical sciences Surfaces Coatings and Films Adsorption Chemical physics Vacancy defect Saddle point Density functional theory 0210 nano-technology Hydrogen embrittlement |
| Zdroj: | Applied Surface Science. 465:833-845 |
| ISSN: | 0169-4332 |
| DOI: | 10.1016/j.apsusc.2018.09.220 |
| Popis: | Vacancy defects on an iron surface have a great influence on the occurrence of hydrogen embrittlement. The adsorption/dissociation mechanism of H2S and the diffusion behavior of H atoms were calculated by first-principles spin-polarization density functional theory (DFT) on defect-free and vacancy-defective Fe(1 0 0) surfaces. The results show that the maximum dissociation energy barriers of H2S on the Fe(1 0 0) surface of defect-free and first-layer vacancy-defective Fe are 0.35 and 0.17 eV, respectively, indicating that the reactivity of the vacancy-defective Fe(1 0 0) surface is moderately increased. The existence of vacancy defects changes the preferential H atom diffusion entrance to the subsurface and shortens the diffusion path. For H diffusion in bulk Fe(1 0 0), it is found that H atoms diffuse via a tortuous path from one tetrahedral-site to a neighboring tetrahedral-site rather than diffusing through a linear trajectory. Moreover, the previously suggested path via the octahedral site is excluded due to its higher barrier and the rank of the saddle point. Diffusion barriers computed for H atom penetration from the surface into the inner-layers are approximately 0.54 eV (except for second-layer vacancy defects), which are all greater than the activation energy for dissociation of H2S on the Fe(1 0 0) surfaces. This suggests that H diffusion is more probable than H2S dissociation as the rate-limiting step for hydrogen permeation into the bulk Fe(1 0 0). |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect