合成气和硫化氢气氛下Rh表面扩散的密度泛函理论研究（英文）

Effects of Syngas and H_2S Atmosphere on Rh Surface*Diffusion:a DFT Study

为了探究Rh催化剂的烧结现象及提高催化剂的稳定性,采用密度泛函理论研究了不同温度下CO,H_2和H_2S气氛下Rh物种在Rh(111)表面上的扩散速率。结果表明:在CO和H2气氛下,随着温度的升高,Rh-CO和Rh-H复合体的迁移速率增大,CO和H_2加速了Rh表面物种的扩散,进而促进了Rh的烧结;在H2S气氛下,Rh-S复合体的形成能是负值,Rh表面上非常容易形成Rh-S复合体。尽管H_2S的浓度仅为几个10-6数量级,但是Rh-S复合体的迁移速率远远大于Rh团簇、Rh-CO和Rh-H复合体的迁移速率。因此,Rh催化剂对H2S极其敏感,表现出较低的耐硫性。

To understand the sintering and improve the stability of Rh catalyst, the diffusion of Rh species on Rh(111) surface under CO, H2 and H2S atmospheres at different temperatures were investigated using density functional theory. Under CO and H2 atmosphere, as the temperature increases, the diffusivity of Rh-CO and Rh-H complex becomes faster than that of Rh adatom, which indicates that CO and H2 can accelerate Rh surface diffusion and promotes the sintering of Rh catalyst. In H 2S atmosphere, the negative formation free energies of Rh-S complexes indicate that Rh-S complexes are easy to form on Rh(111) surface. Compared with that of Rh species, Rh-CO and Rh-H complex, the diffusivity of RhS complex is very large at 10^-6 level of H2S. Therefore, Rh catalyst is extremely sensitive to the S-containing species and has lower sulfur tolerance.