DFT study of SF₆ adsorption by Pd-doped hydroxyl-terminal modified Ti₃C₂T_x MXene

SF₆ gas has a strong greenhouse effect, and how to treat SF₆ in an environmentally friendly way has been a hot topic of current research. In this paper, the adsorption behavior of SF₆ on the surface of Pd-doped hydroxyl-terminated modified Ti₃C₂T_x (i.e., Ti₃C₂(OH)₂) was investigated based on the density functional theory using two-dimensional MXene as the catalyst. The structures of different Pd-doped Ti₃C₂(OH)₂ were analyzed and the most structurally stable doped structures were selected as the basis for subsequent calculations. A large number of adsorption configurations were constructed and geometrically optimized, and the adsorption energy, charge transfer, differential charge density, and density of states of the systems were calculated in order to analyze the gas-solid interactions and find the surface active sites; compared with the adsorption performance of undoped Ti₃C₂(OH)₂ on SF₆, it was found that Pd doping played a less inhibitory role in the adsorption of SF₆ on the Ti₃C₂(OH)₂ surface. The results of this study can provide theoretical support for the use of Pd-doped Ti₃C₂(OH)₂ as a catalyst for the degradation of SF₆.

In this paper, simulations of SF₆ adsorption on Ti₃C₂T_x surfaces are based on density functional theory and are carried out in the Dmol³ module of Material Studio. To better describe the non-uniform electron density of the actual system, the PBE functional in the generalized gradient approximation (GGA) was chosen for the optimization of the structure of the gas-solid interface system and the calculation of the relevant electronic properties, combined with the Grimme dispersion correction in the DFT-D dispersion correction for the electron exchange correlation term. Because both Pd and Ti are transition metal elements, the mode-conserving pseudopotential DNP basis set containing relativistic effects was chosen for the electronic wave function expansion. In this paper, an all-electron model is used for the inner core treatment of gas molecules and a density generalized semi-nuclear pseudopotential DSSP is used for the solid surface treatment.