Synergistic enhancement of gas sensor performance in Janus PtSSe monolayer via Pd/Rh decoration and strain engineering: a first-principles investigation

Employing density functional theory (DFT), this work proposes decorating PtSSe monolayer with transition metals Pd or Rh separately, combined with strain engineering, to regulate and enhance sensing performance for three toxic gases (CO, NO₂, SO₂). Systematic analysis of adsorption energy (E_ads), charge transfer (Q_t), charge density difference (CDD), band structure, density of states (DOS), sensitivity (S), and recovery time (τ) reveals that Pd and Rh atomic decorations significantly improve the PtSSe monolayer's adsorption and sensing performance for CO, NO₂, and SO₂. Further strain calculations demonstrate that biaxial strain considerably modulates the gas-sensing performance of Pd- and Rh-decorated PtSSe. Specifically, a −2% compressive strain enhances the sensitivity of the Pd-PtSSe monolayer toward SO₂ from 172% to 466% while reducing its recovery time by 63.8%, thereby improving the reusability of the sensor. Additionally, analysis of CDD indicates that, within our computational model system, Hirshfeld population analysis provides more physically reliable results than Mulliken analysis. These findings provide theoretical support for the synergistic strategy of transition metal functionalization and strain engineering in Janus PtSSe systems, thus offering important design guidance and valuable insights for the optimization of gas sensor performance in practical applications.