Construction of 1T/2H-MoS2/MoO2 Heterojunction via Mild Oxidation with Sodium Percarbonate for Rapid, Low RMSnoise, and Highly Sensitive NO2 Detection

Abstract

To address the challenge of achieving ultra-trace level NO2 detection with fast recovery kinetics, this study employed a mild chemical oxidation strategy with sodium percarbonate to achieve modification for 1T/2H mixed-phase MoS2. Characterization techniques including XRD, Raman, XPS, SEM, and TEM collectively confirmed the successful fabrication of 1T/2H-MoS2/amorphous MoO2 heterojunctions. At 10 ppm NO2 concentration, the composite material exhibited a response value of 421.66%, with response/recovery times of 14/11 s, and a theoretical detection limit of 9.43 ppt. The dynamic properties of the composite material were significantly superior to those of pure MoS2. Systematic mechanistic investigations (NO2-TPD, EPR, and DRIFTS) revealed that the introduced amorphous phase and Mo5+ paramagnetic centers effectively modulated the adsorption energy of NO2. By applicably passivating the sulfur active sites on the 1T-MoS2 edges, the 1T/2H-MoS2/MoO2 heterojunction provided a moderate adsorption strength for the NO2 molecule, enabling rapid and reversible gas-sensing kinetics while maintaining a high sensitivity and an extremely low theoretical detection limit. A combined analysis of the band structures with UV–vis and UPS spectroscopy confirmed that the formation of an intrinsic electric field within the heterojunction and the optimization of the electronic structure not only facilitated ultrafast charge transfer at the interface but also significantly suppressed background noise. This innovation enabled highly sensitive, ultrafast, and reversible detection. This study proposes an effective regulation strategy for electronic and surface structures, providing a rational design framework for high-performance MoS2-based gas sensors.