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

Abstract

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 SF 6 decomposed gases (SOF 2 , SO 2 , and H 2 S) on Ti 3 C 2 O 2 , Ti 3 C 2 F 2 , and Ti 3 C 2 (OH) 2 . Modification of the surface of Ti 3 C 2 O 2 and Ti 3 C 2 F 2 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 Ti 3 C 2 O 2 and Ti 3 C 2 F 2 , the SOF 2 , SO 2 , and H 2 S gas molecules tend to be chemisorbed on Ti 3 C 2 O 2 and Ti 3 C 2 F 2 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 Ti 3 C 2 O 2 and Ti 3 C 2 F 2 with point vacancy are feasible novel sensing materials to detect SF 6 decomposed species with high sensitivity and low electronic noise. The sensitive detection capability of SO 2 is particularly noticeable.

Computational Screening of Ti3C2TX MXene by Controlling the Functionalized Catalyst for NH3 Gas Sensor

“…When the value of ELF (>0.5), it represents a covalent bond or core electron, and when its value (<0.5), it represents an ionic bond. [15,33] Figure 6a-c is the ELF diagrams of Ti 3 C 2 O 2 , Ti 3 C 2 F 2 , and Ti 3 C 2 H 2 . It can be seen from the diagram that the ELF value of T X (T X = ÀO, ÀF, ÀH) atoms is about 0.5, and electrons similar to electron gas are formed nearby pair distribution.…”

“…[ 25 ] The 2D host Ti 3 C 2 T X (T X = O, F, H, S, Cl) was simulated in Materials Studies 8.0 using a 3 × 3 × 1 supercell. [ 15 ] A vacuum layer thickness of 20 Å was used to avoid adjacent Ti 3 C 2 T X interactions. [ 9 ] The plane wave was expanded with a cutoff energy of 520 eV.…”

“…[10][11][12] Recently, MXenes have attracted much attention in the field of gas sensors due to their excellent metallic conductivity, [13] oxidation resistance, [14] layered structure with anisotropic properties, [11] and high surface area. [15] Even the member Ti 3 C 2 T X can have various functional groups (T X = O, OH, and F), and some new surface functional groups (T X = H, S, Cl, Se, Br, Te, and NH) have appeared in succession. [16] It is well known that the key step of heterogeneous catalytic reactions is the adsorption and activation between the gas molecules and the functionalized surface catalysts of sensing materials.…”

From Single Atom to Low-Nuclearity Cluster Immobilized Ti3C2TX MXene for Highly Efficient NO Electroreduction to NH3

“…The energy and force convergence thresholds on each atom were set to 10 –4 eV and 0.01 eV/Å, respectively. To facilitate the screening of single and cluster metal atoms, 3 × 3 × 1 supercell of Ti 3 C 2 O 2 with a z -direction of 25 Å was built to investigate the NORR. , The thermal stability was investigated by the CPMD simulations in the NVT ensemble for 5 ps with a time step of 0.1 fs. The annealing temperatures were set to 300 and 600 K using the Nosé–Hoover thermostat method .…”

Effect of Transition Metal (Hf and Cd) Doping/Codoping on Ti3C2O2 MXene as NH3 Sensor: First Principles

“…Based on previous studies, an effective method to understand the electronic behavior of adsorption system is partial density of states (PDOS) analysis. [39,40] To understand the electronic structure changes due to Hf or Cd monodoped Ti 3 C 2 O 2 , codoped Ti 3 C 2 O 2 , and their adsorption systems of NH 3 molecules, the density of states were calculated as shown in Figure 4. From Figure 4a, the total density of states is mainly contributed by Ti 3d, C 2p, and O 2p orbitals between À12 and 4 eV.…”