基于第一性原理计算硫化氢(H2S)在Pt-graphene上的吸附性能和解离机理

A theoretical study of H2S adsorption and dissociation mechanism on defected graphene doped with Pt

通过第一性原理计算研究了四种Pt或Pt团簇修饰石墨烯材料的几何结构、电子结构及其对硫化氢(H_(2)S)分子吸附、分解行为。结果表明,H_(2)S在四种材料上均为弱的物理吸附,但H_(2)S分解后的HS和S可以稳定吸附在材料表面。对于H_(2)S的分解过程,考虑了三个基本过程:(Ⅰ)H_(2)S(g)→H_(2)S(ads);(Ⅱ)H_(2)S(ads)→HS(ads)+H(ads);(Ⅲ)HS(ads)→H(ads)+S(ads)。H_(2)S在四种不同表面的第一H–S键断裂能垒分别为1.69、0.52、0.01和0.24 eV;H–S中断裂第二H–S键的能垒分别为2.34、1.08、0.81和1.12 eV。因此,H_(2)S完全解离的控制步骤是第二个H–S键断裂过程。结合H_(2)S吸附和分解结果研究发现,单Pt原子掺杂缺陷石墨烯有利于吸附H_(2)S,但对解离不利;Pt团簇掺杂的空位较大的缺陷石墨烯能够轻松吸附并消除H_(2)S分子,有望成为吸附、分解H_(2)S气体的理想材料。

The adsorption and dissociation of hydrogen sulfide(H_(2)S)molecule on Pt or Pt4 cluster doped graphene with different vacancy(VG),as well as their geometric and electronic structures have been investigated by density functional theory(DFT).It has found that H_(2)S and H atom are weakly adsorbed on Pt/Pt4-VG,while HS and S atom are strongly chemisorbed on different surfaces.By using climbing nudged elastic band method(CI-NEB),three elementary processes have been studied:(Ⅰ)H_(2)S(gas)→H_(2)S(ads);(Ⅱ)H_(2)S(ads)→HS(ads)+H(ads);(Ⅲ)HS(ads)→H(ads)+S(ads).The energy barriers to break the first H-S bond in H_(2)S on four different surfaces(Pt-MVG,Pt-DVG,Pt4-MVG,Pt4-DVG)are 1.69,0.52,0.01 and 0.24 eV respectively.In contrast,the energy barriers to break the second H-S bond in HS are 2.34,1.08,0.81 and 1.12 eV respectively.It is suggested that the control step of the complete dissociation of H_(2)S is the second H-S bond rupture process.The trend shown in this study reveals that single Pt atom doped defected graphene is favored for adsorption of H_(2)S,but is disadvantage for dissociation.Pt cluster doped defected graphene with bigger vacancy can successfully adsorb and easily eliminate H_(2)S molecule,which is expected to be the ideal material for the adsorption and dissociation.