Unlocking the sensing and scavenging potential of Sc₂CO₂ and Sc₂CO₂/TMD heterostructures for phosgene detection

The detection of phosgene is critically important owing to its extreme toxicity and potential use as a chemical warfare agent to ensure public safety and security. Two-dimensional (2D) scandium carbide MXenes (Sc₂CT; T = O^-, x = 2) stand out as promising materials for gas sensing applications owing to their unique electronic and adsorption properties. In this study, first-principles calculations based on the GGA-PBE functional were employed to investigate the structural, electronic, and mechanical characteristics of Sc₂CO₂ with different surface termination positions. The adsorption behavior of Sc₂CO₂ was systematically explored for various gas molecules, including N₂, O₂, CO, NO, CH₄, H₂S, and, notably, phosgene (COCl₂). Specifically, phosgene exhibited a high adsorption energy, highlighting the selectivity of Sc₂CO₂ towards this toxic gas. Furthermore, the impact of gas adsorption on the electronic structure of Sc₂CO₂ was investigated. Strategies such as increasing the operating temperatures and forming heterostructures with transition metal di-chalcogenides (MoSe₂ and WSe₂) proved to be highly effective to mitigate the challenges related to slow recovery time. Thus, this work underscores the potential of Sc₂CO₂ MXenes as highly sensitive and selective gas sensors, particularly for phosgene sensing.