A computational study of adsorption of H₂S and SO₂ on the activated carbon surfaces

An effort has been made to explore the adsorption potential of activated carbon (AC) structures for adsorption of hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) employing density functional theory (DFT) at GGA level. 2-ring, 3-ring, 6-ring, and 9-ring carbon structures are used as adsorbent surfaces. The above mentioned rings are examined by creation of defect and inclusion of hydrogen as well to get the clear view close to experimental observations of adsorption properties of activated carbon. The adsorption properties depend upon many factors including whether adsorbate adsorbs in planer or non-planer mode, defect creation in the adsorbent substrate, atomic hydrogen insertion in the system and size of the adsorbent system. Our calculations show that side by side (planer) interaction binds the molecules much more strongly in comparison with molecules adsorbed upon the surface in non-planer mode. If vacancy is created at the central position of the surface, the molecules bind with substantial binding energy. However, overall E_ads of the molecules varies randomly and no consistency could be achieved. Additionally, smaller sized structures are favorable relative to the bigger surfaces. The highest E_ads for both the molecules is -2.97 eV, though not on the same substrate system. Finally, it can be argued that activated carbon is very useful material for adsorbing the noxious gases.