A DFT study on the adsorption of various mercury species in the coal combustion flue gases on the Mo-doped Fe3O4(111) surface
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摘要: 利用CASTEP软件包采用密度泛函理论计算研究了过渡金属Mo掺杂Fe3O4(111)Fetet表面对Hg0、HgCl和HgCl2的吸附特征,分析了Mo掺杂前后Fe3O4(111)Fetet表面上不同汞物种的吸附形态。结果表明,Mo掺杂Fe3O4(111)Fetet表面对HgCl和HgCl2为化学吸附,而对Hg0的吸附为物理吸附;与纯净表面相比,HgCl在Mo原子掺杂表面上的吸附能提高了40%-66%。HgCl2在纯净Fe3O4(111)Fetet表面形成"M"形结构;而掺杂Mo原子后,由于Cl原子与Mo原子之间更强的相互作用,使得HgCl2发生了完全解离,两个Cl原子分别与Mo原子和Fe原子成键吸附在表面,Hg脱附。相关研究结果可为脱除燃煤烟气中的汞提供一定的理论指导。
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关键词:
- 汞 /
- 密度泛函理论 /
- Mo掺杂 /
- Fe3O4(111)表面 /
- 吸附
Abstract: The adsorption characteristics of Hg0, HgCl and HgCl2 on the Mo-doped Fe3O4 (111) Fetet surface were investigated by density functional theory (DFT) calculation with the CASTEP software package. The results indicate that both HgCl and HgCl2 are chemically adsorbed on the Mo-doped Fe3O4 (111) Fetet surface, whereas Hg0 is bound to the surface by physisorption. The binding energies of HgCl on the Mo-doped Fe3O4 (111) Fetet surface is about 40%-66% higher than that on the pure Fe3O4 (111) Fetet surface. For the adsorption of HgCl2 molecule on the pure Fe3O4 (111) Fetet surface, two Cl atoms interact with one Mo atom and one Fe atom, forming the "M" structure; in contrast, on the Mo-doped Fe3O4 (111) Fetet surface, the stronger interaction between Cl atom and Mo atom allows a complete dissociation of HgCl2 and release of Hg. The adsorption mechanism of mercury species on the Mo-doped Fe3O4 (111) Fetet surface revealed in this work may be helpful for the practical removal of mercury from coal-fired flue gases.-
Key words:
- mercury /
- density functional theory /
- Mo doped /
- Fe3O4(111) surface /
- adsorption
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表 1 Hg0在Fe3O4(111)和Mo/Fe3O4(111)表面的稳定构型参数
Table 1 Optimized parameters for Hg0 on theFe3O4(111) and Mo/Fe3O4(111) surfaces
Adsorption side Eads/(kJ·mol-1) RHg-X/nm QHg/e 1×1 A Fe Top -38.10 0.278 0.19 B Mo Top -33.64 0.298 0.11 2×1 C Mo Top -27.34 0.296 0.16 D Fe Top -29.58 0.279 0.20 Eads denotes adsorption energies, RHg-Mo and RHg-Fe denote distances between adsorbed Hg and Mo/Fe, respectively, QHg denotes Mulliken charge of Hg atoms 表 2 HgCl在p(1×1) Fe3O4(111)和Mo/Fe3O4(111)表面的稳定构型参数
Table 2 Optimized parameters for HgCl on the p(1×1) Fe3O4(111) and Mo/Fe3O4(111) surfaces
Eads/(kJ·mol-1) RCl-X/RHg-X/nm RHg-Cl/nm QHg/e QCl/e Fe3O4(111) Fetet 1A -135.18 -/0.255 0.235 0.37 -0.31 1B -214.21 0.224/- 0.353 0.12 -0.30 1C -137.22 -/0.208 0.228 0.70 -0.27 Mo/Fe3O4(111) Fetet 1D -224.47 -/0.268 0.234 0.30 -0.33 1E -332.78 0.224/- 0.384 0.02 -0.21 1F -93.82 -/0.210 0.230 0.59 -0.26 表 3 HgCl在p(2×1) Fe3O4(111) Fetet和Mo/Fe3O4(111)表面的稳定构型参数
Table 3 Optimized parameters for HgCl on the p(2×1) Fe3O4(111) and Mo/Fe3O4(111) surfaces
Eads/(kJ·mol-1) RCl-X/RHg-X/nm RHg-Cl/nm QHg/e QCl/e Fe3O4(111) Fetet 2A -265.59 0.215/0.273 0.500 0.28 -0.36 2B -211.21 0.214/- 0.334 0.07 -0.31 2C -137.90 -/0.255 0.236 0.39 -0.32 2D -141.63 -/0.208 0.228 0.70 -0.28 Mo/Fe3O4(111) Fetet 3A -371.56 0.226/0.273 0.600 0.23 -0.26 3B -340.62 0.225/- 0.402 0.04 -0.22 3C -257.23 0.297/0.215 0.420 0.26 -0.37 3D -337.09 0.224/- 0.353 0.01 -0.21 3E -213.25 -/0.214 0.368 0.02 -0.33 3F -229.42 -/0.268 0.234 0.34 -0.35 3G -130.29 -/0.255 0.237 0.32 -0.34 3H -118.30 -/0.208 0.230 0.66 -0.28 3I -111.35 -/0.209 0.229 0.63 -0.27 表 4 HgCl2在p(2×1) Fe3O4(111)和Mo/Fe3O4(111)表面的稳定构型参数
Table 4 Optimized parameters for HgCl2 on the p(2×1) Fe3O4(111)Fetet and Mo/Fe3O4(111)Fetet surfaces (2×1 surface cell)
Eads/(kJ·mol-1) RCl1-X/Cl2-X/Hg-X/nm RHg-Cl1/RHg-Cl2/nm Angle/(°) QHg/e QCl1/QCl2/e Fe3O4(111) Fetet 4A -165.81 0.231/0.233/- 0.254/0.249 137.68 0.73 -0.30/-0.30 4B -32.86 0.233/- 0.229/0.236 178.68 0.74 -0.29/-0.37 Mo/Fe3O4(111) Fetet 4C -290.18 0.214/0.223/- 0.345/0.366 124.36 0.04 -0.31/-0.17 4D -6.55 -/-/0.293 0.233/0.232 174.07 0.60 -0.35/-0.35 4E -85.71 -/0.227/- 0.241/0.307 179.70 0.35 -0.29/-0.25 4F -22.30 -/0.237/- 0.232/0.242 179.29 0.66 -0.29/-0.38 -
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