H2S adsorption on graphene in the presence of sulfur: A density functional theory study

Abstract

The high affinity of graphene for H2S makes it a potential adsorbent for separating H2S from industrial waste gas streams, and for its use in H2S sensors. The gas streams containing H2S also contain S atoms that can get bonded to graphene during adsorption. Moreover, at high temperatures, H2S dissociate at graphene defects leading to H2 desorption with S atom remaining on graphene. This study reports the effect of the presence of S atom on graphene on H2S adsorption using plane-wave density functional theory to assess the suitability of graphene-based adsorbents for continuous H2S capture. During H2S interaction with pristine graphene with S atom bonded to it, a surface cleaning mechanism was observed, where H2S exothermically removed S atom by forming H2S2. When S atom was doped in the single-vacancy defect of graphene, both physisorption and chemisorption of H2S was observed. The adsorption energy released during H2S physisorption on S-doped graphene was comparable to that for pristine graphene. However, during chemisorption, H2S dissociated on S-doped graphene to form HSSH bonded to graphene with the release of a high amount of energy. The results suggest that S atom in single-vacancy defects can enhance H2S capture on graphene.