Edge-Enriched Mo2TiC2Tx/MoS2 Heterostructure with Coupling Interface for Selectively NO2 Monitoring

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.

Automated summary

This study proposes a highly active double transition metal titanium molybdenum carbide (Mo2TiC2Tx) with strong surface adsorption for NO2 gas sensing and further couples it with molybdenum disulfide (MoS2) to construct an edge-enriched heterostructure. The Mo2TiC2Tx/MoS2 gas sensor exhibits outstanding response and selectivity towards NO2 due to its strong adsorption, rich adsorption sites, and coupling interface. It also demonstrates sensitivity, detection limit, and reversibility at room temperature, making it suitable for gas leakage detection and dangerous warning.