Fabrication and characterization of a high-surface area MoS2@WS2 heterojunction for the ultra-sensitive NO2 detection at room temperature

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have to date stimulated increasing research interest in the field of gas sensing due to their high surface to volume ratio, tunable layer-dependent electronic properties and wide range of catalytic performance. However, their poor gas sensing performance at room temperature (RT), resulting in incomplete recovery, long response time and low response, hinders the practical applications of pristine TMD (MoS2 and WS2) gas sensors. Herein, we demonstrated the synthesis of a heterojunction of few-layer MoS2 nanosheets (NSs) with multilayer WS(2)via a simple one-pot hydrothermal process and successfully improved the gas sensing performance of TMD heterostructure nanomaterials (NMs) for NO2 at RT. The pristine MoS2 NSs exhibited a sluggish response (R-a/R-g = 2.7 to 50 ppm) with incomplete recovery to NO2 gas. After WS2 functionalization, the MWS-2 (the atomic ratio of Mo:W was about 1.55:1) sensor showed a dramatically enhanced response (26.12 to 50 ppm) with a short response time (1.6 s), excellent base line recovery (27.7 s), commendable selectivity and appreciable stability to NO2 gas, which could be attributed to the synergistic effect between MoS2 and WS2 NSs originating from the enhanced surface area and remarkably increased exposed active sites for NO2 adsorption. Our results demonstrate that the proposed facile method is a promising strategy to improve the gas sensing performance of 3D flower-like MoS2@WS2 at RT and can also be extended to other TMD-based devices.