Effect of surface functional group over tungsten carbide MXene for efficient NH3 gas sensing using density functional theory

Detecting and sensing NH3 as a pollutant gas is absolute necessity in controlling the excess emission from industries, for indoor air quality supervision, medical and environmental monitoring. 2D materials such as MXene have been explored in the field of gas sensing due to their large surface-to-volume ratio, presence of large number of adsorption sites, mechanical flexibility, rapid charge carrier migration and high conductivity. Present investigation on W2CT2 (T: O, F) includes structural and electronic properties towards NH3 adsorption using density functional theory. Various configurations of termination group, NH3 adsorption over different sites along with different orientations of NH3 molecules considering N-lone pair (LP) and H-1s & O/F-2p orbital interaction have been computed for energetic stability. Values of adsorption energies, charge transfer, charge accumulation over the MXene and formation of interfacial electric field indicate strong physisorption and short recovery time of NH3 gas molecule over W2CT2. Significant change in electrical conductivity after NH3 adsorption, formation of Hydrogen bond between NH3 and MXene and its strength attributes to the variation of electronic, transport and adsorption properties with varying NH3 concentration signifies W2CT2 (T: O, F) as promising 2D material for NH3 gas sensing.