Synergistic mechanisms in CuO/GeC for selective gas sensing of atmospheric pollutants under humid and oxidative conditions: A DFT study.

In this work, based on density functional theory (DFT), we systematically investigate the effect of CuO modification on the adsorption performance of a two-dimensional GeC monolayer toward typical pollutant gases (CO, NH3, NO2, SO2), and explore the regulatory mechanisms of H2O/O2 competitive adsorption, biaxial strain (-6% to 6%), and an external electric field (-0.6 to 0.6 eV/Å). The results show that the pristine GeC exhibits low adsorption energies (-0.125 to -0.591 eV) for the gas molecules, dominated by weak physisorption. After CuO modification, Cu atoms become highly active sites, significantly enhancing the gas adsorption capacity, with adsorption energies increased to -0.334 to -1.954 eV. Among the gases, NO2 shows the strongest adsorption (-1.954 eV), and the system exhibits clear selectivity. Pre-adsorption of H2O and O2 reduces the adsorption energy of the target gases through site competition and orbital hybridization, but the interference with NH3 and NO2 is relatively weak. Both biaxial strain and external electric field can effectively tune the adsorption strength; the adsorption energy is significantly enhanced under a strain of -2% to 4% or a negative electric field. Calculations of recovery time indicate that CuO/GeC shows rapid CO desorption at room temperature, whereas NH3, NO2, and SO2 desorb slowly. Moderate heating enhances its reversibility. This work provides a theoretical foundation for developing high-performance, selective, and anti-interference CuO/GeC gas sensors. Notably, at room temperature, NH3 and NO2 exhibit extremely long recovery times (4.82×1012 s and 1.08×1021 s, respectively), indicating irreversible adsorption behavior that makes them suitable for high-sensitivity single-use detection, whereas CO and SO2 are more appropriate for reversible sensing.