Investigation of CO2, NO2, SO2, and H2O Gas Adsorption on Al2O3, TiO2, and SiO2 Surfaces

This study presents a unified first-principles investigation of CO2, NO2, SO2, and H2O adsorption on Al2O3 (001), TiO2 (001), and SiO2 (001) surfaces, establishing the first cross-material, chemically consistent benchmark for oxide–gas interactions. Calculated adsorption energies reveal strong chemisorption of SO2 and NO2 on Al2O3 and TiO2, moderate H2O binding—particularly on TiO2 where hydroxylation is favored—and generally weak CO2 interactions across all surfaces. Bader charge analysis provides atom-resolved insight into these trends, showing substantial electron transfer and pronounced oxygen-site polarization for strongly adsorbing gases, in contrast to the minimal charge redistribution characteristic of physisorbed CO2. These charge-transfer signatures distinguish binding mechanisms, clarify the origins of material-specific selectivity, and link adsorption to expected variations in surface conductivity and sensor response. The combined energetic and electronic analysis also reveals competitive effects between humidity and CO2 on surface hydroxylation and local electronic structure, a phenomenon critical for realistic sensing environments but previously unaddressed. Overall, this work delivers a rigorous comparative framework for understanding gas interactions with technologically relevant oxides and provides a solid foundation for future studies involving defects, dopants, surface reconstructions, and advanced functionalization strategies for environmental monitoring and energy-conversion devices.