Edge-Enriched Mo<inf>2</inf>TiC<inf>2</inf>T<inf>x</inf>/MoS<inf>2</inf> Heterostructure with Coupling Interface for Selectively NO<inf>2</inf> Monitoring

Abstract

Endowed with rich terminal groups, good electrical conductivity, and controllable structure, transition metal carbides/nitrides (MXenes) have attracted extensive attention for potential application in gas sensor, but long-standing challenges of the MXenes (titanium carbide as the representative) are their limited selectivity and sensitivity. Herein, a high-active double transition-metal titanium molybdenum carbide (Mo2TiC2Tx) with superstrong surface adsorption (−3.12 eV) for NO2 gas molecule is proposed, and it is further coupled with molybdenum disulfide (MoS2) by interface modulation to construct an edge-enriched heterostructure. Due to the synergistic effect of strong adsorption, rich adsorption sites, and coupling interface of Mo2TiC2Tx/MoS2 composite, the as-fabricated Mo2TiC2Tx/MoS2 gas sensor exhibits an outstanding response toward NO2 with high selectivity against various interference gases, which is well supported by density functional theory calculations. Meanwhile, the sensor exhibits a sensitivity of 7.36% ppm−1, detection limit of 2.5 ppb, and reversibility at room temperature. A portable, wireless NO2 monitoring system is demonstrated for gas leakage searching and dangerous warning based on Mo2TiC2Tx/MoS2 gas sensor. This work facilitates the gas sensing application of MXenes, and provides an avenue for the development of wireless sensing system in environmental monitoring and safety assurance.