Tailoring gas adsorption and multifunctional properties of Na-decorated GaP/silicene heterostructure for sensing and thermoelectric applications

The adsorption of technologically relevant gas molecules (NH3, CO2, H2, H2O, O2, NO2, CO, and SO2) on a Na-decorated GaP/silicene heterostructure is systematically investigated using first-principles calculations combined with CGCNN predictions. All molecules exhibit negative adsorption energies, with NO2, SO2, and NH3 showing the strongest binding. NO2 and SO2 induce spin polarization and finite magnetic moments, governed by charge transfer and orbital hybridization. Gas adsorption significantly modulates optical and thermoelectric responses, particularly in the low-energy region. CGCNN results reveal a reduction in mechanical stiffness (B, G), most pronounced for NO2, alongside a slight increase in Debye temperature, while the thermal expansion coefficient remains nearly unchanged (~6.0×10-5 K-1), indicating preserved lattice anharmonicity. These findings highlight the potential of this heterostructure for selective gas sensing and thermoelectric applications.