Sulfur filling in oxygen vacancy and modulating surface active site on molybdenum-based transition metal oxides/sulfides heterostructure for room-temperature chemiresistive NO2 detection

Constructing distinctive heterogeneous structures and surface site activation represents an effective strategy for enhancing the gas identification capability with reinforced strength. In the previous study, it has been demonstrated that the formation of oxygen vacancies (VO) in heterostructure can significantly enhance metal oxidebased gas sensing. However, developing techniques that effectively modulate VO while simultaneously increasing active sites is a critical yet challenging endeavor. Herein, we designed a hierarchical hollow MoO3 @CoMoO4@CoMoS3.13 heterostructure through post-calcination and vulcanization methods. The results of X-ray adsorption spectroscopy and density functional theory show that the obtained hierarchical heterostructure can significantly accelerate the transport of electrons. Also, the introduction of S atom can modulate VO by tuning the local electronic structure and simultaneously inducing charge compensation at the unsaturated coordination site of cobalt around VO. The reduction of charge density at the exposed Co sites further imparts the heterostructure prominent target gas adsorption properties. Thus, the MoO3@CoMoO4 @CoMoS3.13 sensor exhibits high-efficient NO2 gas sensing performance at room temperature with an impressive response value of 35.42 (50 ppm, S = Ra/ Rg), speedy response time of less than 1.1 s, as well as a remarkable long-term stability for at least 60 days.