单原子Pt增强α-Mo_2C(0001)抗硫中毒特性机理的第一性原理研究

First principles study on the mechanism of improving sulfur tolerance of α-Mo_2C( 0001) by single atom Pt

采用基于密度泛函理论(DFT)第一性原理方法研究了α-Mo_2C(0001)表面和Pt/α-Mo_2C(0001)表面抗硫中毒特性及其机理.发现干净的Mo_2C(0001)表面对含硫物种(S、HS和H2S)吸附很强(吸附能分别为-6.46、-4.15和-1.54 e V),极易S中毒.Pt的引入可以减弱含硫物种在Mo_2C(0001)表面的吸附,当含硫物种在Pt/Mo_2C(0001)表面Pt原子周围吸附时吸附能较小,在Pt原子顶位吸附时吸附能最小,远离Pt原子吸附时吸附能增大.因此,Pt的引入对Pt周围催化活性位点避免硫原子中毒起到很好的保护作用,达到抗硫中毒效果.预期提高Pt原子覆盖度,可以进一步降低含硫物种与Mo_2C(0001)表面的相互作用,更好地抗硫中毒,为设计高活性、高抗硫中毒性的Mo_2C基催化剂提供理论依据.

The tolerance of sulfur poisoning on both clean α-Mo2C（ 0001） and Pt/α-Mo2C（ 0001） surfaces are investigated using density functional theory（ DFT） calculations with the periodic slab model. It is found that the adsorption of S,HS and H2 S on the clean Mo2C（ 0001） surface is very strong（ with the adsorption energies of-6. 46,-4. 15,and-1. 54 e V,respectively）. The introduction of Pt decreases the adsorption energies of S,HS and H2 S on the Mo2C（ 0001） surface. When the sulfides are adsorbed on the Pt/Mo2C（ 0001） surface around the Pt atom,the adsorption energy of sulfide is decreased and the adsorption on the top position of Pt atom has the smallest adsorption energy. The adsorption energy increases when the sulfides are farther away from Pt. Hence,the introduction of Pt can play an important role in protecting the catalytically active sites around Pt from the sulfur poisoning. It can be anticipated that the effect of sulfur tolerance can be further enhanced by increasing the coverage of Pt on Mo2C（ 0001）. The present study provides guidance for the design of highly active and sulfur tolerant catalysts based on Mo2C.