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

The adsorption and dissociation of hydrogen sulfide (H₂S) 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 H₂S 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) H₂S(gas)→H₂S(ads); (II) H₂S(ads)→HS(ads) + H(ads); (III) HS(ads) → H(ads)+ S(ads). The energy barriers to break the first H–S bond in H₂S 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 H₂S 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 H₂S, but is disadvantage for dissociation. Pt cluster doped defected graphene with bigger vacancy can successfully adsorb and easily eliminate H₂S molecule, which is expected to be the ideal material for the adsorption and dissociation.