Phosgene Gas Sensing of Ti₂CT₂ (T = F⁻, O⁻, OH⁻) MXenes

Abstract

The phosgene gas sensing properties of experimentally produced 2D titanium carbide MXenes with surface terminations (Ti2CT2: T = F−, O−, OH−) are studied by first‐principles calculations. The effect of Ti and C vacancy defects, which are frequently created in synthesizing MXenes, on the structural, mechanical, electronic, and gas adsorption properties are studied to analyze the phosgene gas sensing performance of Ti2CT2 MXenes. Pristine and defective Ti2C, Ti2CF2, and Ti2C(OH)2 show metallicity, making them ideal for gas sensing. Ti (C) vacancy defects in Ti2CO2, Ti2CF2, and Ti2C(OH)2 cause an increase (decrease) in work function, resulting in enhanced interaction between the MXene surface and a gas molecule. When a phosgene gas molecule is exposed on the surface of MXenes, only Ti2C(OH)2 shows stable adsorption and charge transfer. An ultra‐low recovery time, the time between adsorption and desorption of a phosgene gas molecule, is achieved for both pristine and defective Ti2C(OH)2 with Ti vacancy. The results elucidate that a Ti2C(OH)2 based sensor has a high potential for efficient reversible phosgene detection.

A theoretical study of allopurinol drug sensing by carbon and boron nitride nanostructures: DFT, QTAIM, RDG, NBO and PCM insights

“…According to the investigations by S. Thomas and M. A. Zaeem, a short recovery time of an adsorbent is favorable for fabricating an efficient sensing device. 65,66 By considering this issue, we have taken the initiative to evaluate the recovery time by the following equation: 67 here, T is the temperature in Kelvin, κ B is Boltzmann's constant (2.0 × 10 −3 kcal mol −1 K −1 ), and ν the attempt frequency. Practically, an adsorbate molecule can be recovered from the adsorbent by exposing it to ultraviolet (UV) rays.…”

From fundamental to CO2 and COCl2 gas sensing properties of pristine and defective Si2BN monolayers

“…The x, y and z correspond to the total number of Si, B and N atoms in the supercell, and N denotes the total number of atoms in the Si 2 BN-ML supercell. Further, we have followed the method described in several other studies 21,38,51 to compute the vacancy formation energy (E VFE ) of Si 2 BN-ML structures with Si, B and N defects. The E VFE is computed using the following relation:…”

“…The changes in the electrical conductivity are related to the charge transfer between the gas molecules and the Si 2 BN-ML. Besides, an efficient gas sensing performance depends on the quantifiable variations in the electrical conductivity 38,[61][62][63] of Si 2 BN-ML after the adsorption of COCl 2 and CO 2 molecules. In general, the adsorption of COCl 2 and CO 2 molecules on the Si 2 BN-ML can either increase or decrease the conductivity, depending on the rate of charge transfer between the Si 2 BN-ML and these target molecules.…”

“…Besides, it is important to notice that each gas molecule possesses a different operational frequency, 68 and for COCl 2 and CO 2 molecules, it is 3.33 Â 10 13 Hz and 7.14 Â 10 13 Hz, respectively. 69 We then computed the temperature-dependent adsorption energy by keeping the operational frequency as 10 13 Hz, as shown in Table 4 38 Si-doped MoS 2 (10 11 s), 70 Alphthalocyanine (346.8 s), 71 borophene (148 ns), 72 and Al-doped boron nitride nanoflakes (0.18 s). 73 Similarly, the computed recovery time of CO 2 molecule is also lower than that of other nanomaterials such as 1T-HfTe 2 (33.7 ns), 74 SiBi (0.73 ps) 75 and NbSeTe (23.1 and 13.3 ps).…”

“…Similarly, COCl 2 or phosgene gas can be extensively released from industries during the production of isocyanate-based plastics, polymers, pesticides, dyes and pharmaceuticals. 38 Exposure to these toxic gases leads to heart failure, pulmonary edema and breathing difficulties, and these gases are highly harmful to living organisms. 39 Therefore, developing efficient gas sensors using stable and free-standing 2D materials is quite promising for the detection of toxic gas molecules.…”