Titanium Carbide MXene as NH₃ Sensor: Realistic First-Principles Study

Abstract

This work presents a more realistic study on the potential of titanium carbide MXene (Ti3C2T x ) for gas sensing, by employing first principle calculations. The effects of different ratios of different functional groups on the adsorption of NH3, NO, NO2, N2O, CO, CO2, CH4, and H2S gas molecules on Ti3C2T x were analyzed. The results indicated that Ti3C2T x is considerably more sensitive to NH3, among the studied gas molecules, with a charge transfer of −0.098 e and an adsorption energy of −0.36 eV. By analyzing the electrostatic surface potential (ESP) and the projected density of states (PDOS), important physical and mechanical properties that determine the strength and nature of gas-substrate interactions were investigated, and also, the significant role of electrostatic effects on the charge transfer mechanism was revealed. Further, the Bader charge analysis for the closest oxygen and fluorine atoms to NH3 molecule showed that oxygen atoms have 60% to 180% larger charge transfer than fluorine atoms, supporting that Ti3C2T x substrate with a relatively lower ratio of fluorine surface terminations has a stronger interaction with NH3 gas molecules. The calculations show that in the presence of water molecules, approximately 90% smaller charge transfer between NH3 molecule and the Ti3C2T x occurs. Ab initio molecular dynamics simulations (AIMD) were also carried out to evaluate the thermal stabilities of Mxenes. The comprehensive study presented in this work provides insights and paves the way for realizing sensitive NH3 sensors based on Ti3C2T x that can be tuned by the ratio of surface termination groups.

A two-dimensional Ti3C2TX MXene@TiO2/MoS2 heterostructure with excellent selectivity for the room temperature detection of ammonia

“…64 Some studies have also revealed that MXene-based gas sensors show higher adsorption energy for NH 3 than other gases using density-functional theory (DFT). 65,66 In addition, TiO 2 acts as an active catalytic site toward ammonia gas at room temperature. 67 Most importantly, there are lone electron pairs in NH 3 molecules, which usually act as electron donors and can provide more electrons to participate in the sensing process.…”

Prospects and Challenges of MXenes as Emerging Sensing Materials for Flexible and Wearable Breath‐Based Biomarker Diagnosis

“…Moreover, the superiority of MXenes to capture NH 3 can compete with MoS 2 and phosphorene. [ 110 ] Furthermore, these theoretical studies have impacted many experimental works and attracted so much attention since they can open novel emerging applications of MXenes beyond energy storage and conversion. Not long after these predictions, many experimentalists are working toward realizing MXene as NH 3 gas sensing materials.…”

A strategic review of MXenes as emergent building blocks for future two-dimensional materials: recent progress and perspectives

“…37,273 DFT calculations were performed to understand the suitability of M 2 CO 2 (M = Sc, Ti, Zr, Hf) for sensing NH 3 gas and revealed a superior trapping/release of NH 3 on the corresponding substrate. 274 Khakbaz et al 275 studied the efficiency of Ti 3 C 2 T X towards sensing NH 3 in the presence of different water molecules and surface terminations. They observed a 60-180% larger binding energy between Ti sites near the O atoms and NH 3 than that of adjacent F atoms, indicating that the low content of F terminated Ti 3 C 2 T X is preferable for NH 3 sensing.…”