DFT study of sensing properties of defected and transition-metal doped V2CF2 towards CH4

As a new type of gas sensor, MXenes material is of great significance in indoor harmful gas detection. The geometric, electronic, and magnetic properties of CH4 adsorbed on intact, F-vacancy defected, and transition-metal (TMs: Mn, Co, Ni, Zn, Nb, Mo) doped V2CF2 have been investigated based on density functional theory. Perfect V2CF2 and F-vacancy defected substrates exhibited low charge transfer, long adsorption distance, and small adsorption energy for CH4. The adsorption mechanism was physical adsorption. After introducing Co and Ni dopants, the adsorption mechanism of CH4 changed to be chemisorption. Additionally, the asymmetric electron spin distribution between the dopant and V atom caused the substrate to change from being non-magnetic to magnetic, as shown by the electronic density of states diagrams. The hybridization between TM-3d orbitals and the p orbitals of the CH4 molecule significantly improved the adsorption stability. It is hoped that the results could provide ideas for creating new CH4 gas sensors based on MXenes.