Adsorption Mechanism of SF ₆ Decomposed Toxic Gases (H ₂ S, SO ₂ , SO ₂ F ₂ ) on Pt-Modified Janus SnSSe Monolayer: A Density Functional Theory Study

This study explores the sensing capabilities of Pt-decorated Janus SnSSe monolayers toward SF₆ decomposition gases (H₂S, SO₂, and SO₂F₂) using density functional theory (DFT). Findings reveal that the introduction of Pt atoms onto either the S- or Se-terminated surface of the SnSSe monolayer markedly improves both the adsorption strength and structural integrity of the material. Adsorption behavior and underlying sensing mechanisms across different gas-substrate systems were comprehensively investigated by examining adsorption energy, adsorption distance, charge density, density of states, orbital interaction, recovery time, sensitivity, and work function. The results indicate that the pristine SnSSe monolayer exhibits only physical adsorption and is unsuitable for detecting any of the three target gases. In contrast, Pt-modified SnSSe demonstrates significantly enhanced gas adsorption. On the S-surface, adsorption energies for H₂S, SO₂, and SO₂F₂ were -0.981 eV, -0.751 eV, and -0.026 eV, respectively, while on the Se-surface, the values were -0.954 eV, -0.776 eV, and -0.026 eV. At the optimal operating temperature, the recovery time for the Pt-SnSSe(S)/H₂S system is 64.67 s, while the recovery times for Pt-SnSSe(Se) toward H₂S and SO₂ are 26.75 and 13.02 s, respectively. Both modified surfaces exhibited poor adsorption performance toward SO₂F₂. This study offers theoretical insights for designing low-power, high-sensitivity, and fast-response gas sensors used to detect SF₆ decomposition products in gas-insulated switchgear (GIS).