First-principles study of hydrogen sulfide decomposition on Sc-Ti₃C₂O₂ single-atom catalyst

Hydrogen sulfide gas poses significant risks to both human health and the environment, with the potential to induce respiratory and neurological effects, and a heightened fatality risk at elevated concentrations. This article investigates the catalytic decomposition of H₂S on a Sc-Ti₃C₂O₂ single-atom catalyst(SAC) using the density functional theory-based first-principles calculation approach. Initially, the adsorption behavior of H₂S on Ti₃C₂O₂-MXene was examined, revealing weak physical adsorption between them. Subsequently, the transition metal atom Sc was introduced to the Ti₃C₂O₂ surface, and its stability was studied, demonstrating high stability. Further exploration of H₂S adsorption on Sc-Ti₃C₂O₂ revealed direct dissociation of H₂S gas molecules into HS* and H*, with HS* binding to Sc and H* binding to O on the Ti₃C₂O₂ surface, resulting in OH groups. Using the transition state search method, the dissociation of H₂S molecules on the SAC's surface was investigated, revealing a potential barrier of 2.45 eV for HS* dissociation. This indicates that the H₂S molecule can be dissociated into H₂ and S with the action of the Sc-Ti₃C₂O₂ SAC. Moreover, the S atom left on the catalyst surface can aggregate to produce elemental S₈, desorbing on the catalyst surface, completing the catalytic cycle. Consequently, the Sc-Ti₃C₂O₂ SAC is poised to be an efficient catalyst for the catalytic decomposition of H₂S.

The Dmol³ module in Materials Studio software based on density functional theory is used in this study. The generalized gradient approximation method GGA-PBE is used for the exchange-correlation function. The complete LST/QST and the NEB methods in the Dmol³ module were used to study the minimum energy path of the dissociation of hydrogen sulfide molecules on the catalyst surface.