Interface-Sensitized ZnO/WS2 Heterostructures: Surface-Activated Porous Sensitizers for Robust Chemiresistive Gas Sensing

Abstract

Hybridizing transition metal dichalcogenides with metal oxides offers a viable route to overcome their intrinsically limited gas sensitivity by facilitating charge transfer during gas adsorption. Metal–organic frameworks have been employed as templates to derive porous metal oxides with tunable surface activity, a key factor governing gas reaction kinetics. When integrated with transition metal dichalcogenides, metal-organic framework-derived metal oxides serve as efficient electronic sensitizers to enhance gas-sensing performance. Herein, we present the van der Waals heterostructure composed of WS2 nanoflakes and metal-organic framework-derived ZnO nanocubes as a chemiresistive gas sensing layer. The morphology and surface chemistry of porous ZnO nanocubes were tailored via a two-step calcination strategy to optimize surface activity. As a result, the porous ZnO/WS2 heterostructure exhibited a 4.05-fold higher response (Ra/Rg = 12.64) toward 5 ppm NO2 compared with pristine WS2 nanoflakes (Ra/Rg = 3.12) with high selectivity. The improved NO2 sensing properties are attributed to the porous structure and abundant chemisorbed oxygen species of porous ZnO NCs, which facilitate fast NO2 adsorption–desorption kinetics and interfacial charge transfer across the heterointerface of porous ZnO/WS2. By leveraging the tunable surface activity of metal-organic framework-derived porous metal oxides, this work provides a viable strategy for enhancing the sensitivity and selectivity in transition metal dichalcogenide-based chemiresistive gas sensors through rational heterostructure design.