Adsorption and sensing properties of Pt-In2Se3 monolayer toward thermal runaway gases (H2, CO, CO2, CH4, C2H4) in LIBs: A DFT study

The adsorption and sensing properties of pristine α-In₂Se₃ and Pt doped In₂Se₃ monolayers for five thermal runaway gases (H₂, CO, CO₂, CH₄, C₂H₄) have been investigated using density functional theory (DFT). The adsorption energy, charge transfer (Q_T), energy density of states, work function, recovery time and sensing response were compared to elucidate the gas adsorption behavior and electronic properties. The results indicate that, when Pt replaces doping the In₂Se₃(↑) surface, the phase state of α-In₂Se₃ changes, turning into a more stable β phase. However, in the Pt-In₂Se₃(↓) surface, no phase transition was observed in α-In₂Se₃. And for the adsorption of H₂, CO and C₂H₄, the introduction of Pt atoms significantly enhances the adsorption energies. Additionally, the absolute value of the integral crystal orbital Hamiltonian population (ICOHP) is the highest for CO adsorbed on Pt doped In₂Se₃ monolayer systems, with values of −2.73 and −2.77 for the upward and downward polarization directions, respectively. This indicates a stronger interaction between CO and Pt atoms, suggesting an enhanced potential for chemical bond formation at Pt sites. The adsorption of gas molecules has shown pronounced differences in its impact on the work function. The Pt-In₂Se₃(↑) surface exhibits considerable sensitivity to CO and CH₄, resulting in the most significant work function shift (work function shift of CO is 0.14 eV; work function shift of C₂H₄ is 0.3 eV), while its response to H₂, CO₂ and CH₄ is nearly negligible. Meanwhile, the adsorption of C₂H₄ on the Pt-In₂Se₃(↓) yields a significant work function shift of 0.49 eV, further indicating the material's potential for selective detection of specific gases. A comprehensive analysis of adsorption energy and work function further reveals that the Pt-In₂Se₃(↑) surface exhibits the most pronounced gas-sensing properties toward CO (adsorption energy of 1.26 eV and work function shift to 6.01 eV), while the Pt-In₂Se₃(↓) surface shows significant sensitivity to both CO (adsorption energy of 1.34 eV and work function shift to 5.31 eV) and C₂H₄ (adsorption energy of 1.05 eV and work function shift to 5.25 eV). When both sensitivity and recovery characteristics are taken into account, Pt-In₂Se₃ monolayers demonstrate a remarkable negative sensing response towards C₂H₄, with values of −99.61 % for the In₂Se₃(↑) surface and −96.87 % for the In₂Se₃(↓) surface. Furthermore, the recovery time for C₂H₄ on the Pt-In₂Se₃(↑) surface is as short as 4.19 × 10⁻³ s at 498 K, while on the Pt-In₂Se₃(↓) surface it is 4.56 × 10⁻² s. These findings indicate that Pt functionalization not only enables ultrahigh sensitivity but also allows for rapid recovery of the sensor after gas exposure, suggesting that Pt-doped In₂Se₃ monolayers are highly promising candidates for efficient and real-time detection of ethylene. These findings provide a theoretical basis for understanding the microscopic mechanisms of gas detection in In₂Se₃-based sensors and contribute to the design of advanced sensing materials for detecting thermal runaway gases in LIBs.