Adsorption of toxic gases by transition metal doped Ti₂CO₂ MXene: a DFT study

MXenes are a new class of two-dimensional (2D) materials that have attracted significant attention in numerous sensor applications due to their excellent properties. To address the urgent need for the efficient detection of toxic gases (such as CO, NO, SO₂, and HF), the gas-sensing response mechanism of transition metal (TM)-doped MXene Ti₂CO₂ on oxygen-sealed surfaces has been systematically investigated using density functional theory (DFT). In this study, three transition metal dopants, Fe, Co and Ni, are investigated and factors such as the band structure, density of states, adsorption energy and charge transfer are analyzed. Meanwhile, the key performance indicators of the sensor, desorption time and sensitivity are also evaluated. The results show that gas molecules undergo physical adsorption on the pristine Ti₂CO₂ surface. When vacancy defects and TM doping are introduced, physisorption transforms into chemisorption. The density of states analysis reveals that the hybridization between the dopant's 3d orbitals and gas molecules enhances adsorption stability. Vacancies and TM doping enhance the material's responsiveness to toxic gases, and the TM doped system can also selectively detect toxic gases. These research results not only provide a reference for the design and optimization of MXene-based gas sensors, but also have a certain impact on the theoretical model of gas adsorption.