Adsorption of SF₆ Decomposed Species on Ti₃C₂O₂ and Ti₃C₂F₂ with Point Defects by DFT Study

The high specific surface area and electrical conductivity of new 2D metal carbide MXenes make them become a suitable candidate as sensor platform of the gas sensor. Herein, density functional theory (DFT) is implemented to investigate the adsorption of the SF₆ decomposed gases (SOF₂, SO₂, and H₂S) on Ti₃C₂O_2, Ti₃C₂F₂, and Ti₃C₂(OH)₂. Modification of the surface of Ti₃C₂O₂ and Ti₃C₂F₂ by O and F point vacancy, respectively, is then performed to improve the adsorption performance. The band structure, charge density differences, electron localization function (ELF), and projected density of states (PDOS) are investigated to study the adsorption mechanism. The results indicate that as compared with the weak adsorption on pristine Ti₃C₂O₂ and Ti₃C₂F₂, the SOF₂, SO₂, and H₂S gas molecules tend to be chemisorbed on Ti₃C₂O₂ and Ti₃C₂F₂ with point vacancy with high adsorption energies. Furthermore, the study of electronic properties suggests that all adsorption systems show high electronic conductivity and the exposed Ti atoms by point defect mainly contribute to the formation of ionic bond with high adsorption energy. Thus, the present results show that Ti₃C₂O₂ and Ti₃C₂F₂ with point vacancy are feasible novel sensing materials to detect SF₆ decomposed species with high sensitivity and low electronic noise. The sensitive detection capability of SO₂ is particularly noticeable.