Selective NO gas sensing over TiVCO₂ MXene: A realistic computational prediction

Abstract Atmospheric pollution and climate change demand advanced sensing technologies for detecting toxic gases with high sensitivity and selectivity. Two-dimensional MXenes, particularly oxygen-functionalized solid-solution TiVC (TiVCO 2 ), exhibit exceptional tunability in electronic and surface properties, making them promising candidates for gas sensing. This study employs first-principles density functional theory (DFT) based simulations to systematically investigate the adsorption behavior, electronic interactions, and sensing mechanisms of TiVCO 2 toward eight environmentally relevant gases (H 2 , CO, NO, NO 2 , SO 2 , H 2 S, NH 3 , CH 4 ). Structural stability analysis confirms the robustness of TiVCO 2 , with a cohesive energy of −8.426 eV atom −1 , while electronic structure calculations reveal retained metallicity with modified Fermi-level states upon O-functionalization. Among different investigated gases, NO exhibits the strongest yet reversible physisorption (−0.62 eV), accompanied by a significant charge transfer (+0.322 e) and Fermi-level state modulation, making it the most viable target for sensing. In contrast, NH 3 and NO 2 show strong chemisorption but suffer from irreversible structural distortions, while H 2 , CO, SO 2 , H 2 S, and CH 4 exhibit weak physisorption with negligible electronic perturbations. Recovery time analysis further supports NO’s suitability ( τ ∼ 0.03 s at 300 K) compared to other gases. These findings establish TiVCO 2 as a selective NO sensor and provide fundamental insights into MXene-gas interactions for next-generation environmental monitoring technologies.