Optimizing Gas Sensing Performance of Molybdenum Oxide through Oxygen Vacancy Modulation: A Critical Review.

Molybdenum oxide (MoO3) is a promising material for gas sensing due to its unique physicochemical properties, including multiple chemical valence states, high thermal stability, and suitable bandgap. Oxygen vacancies, as critical structural defects, significantly enhance the gas sensing performance of MoO3 by modifying its electronic structure and surface chemistry. This review discusses the formation mechanism of oxygen vacancies and their role in improving sensing performance, such as introducing energy levels within the bandgap, altering surface atomic configurations, and promoting gas adsorption and reactions. Experimental and theoretical studies demonstrate that oxygen vacancies enhance sensitivity and selectivity for gases like NH3, NO2, H2S, TEA, and ethanol. Strategies to optimize oxygen vacancy (OV) concentration, including doping with metal/rare earth elements and microstructure design, are also explored. Future research directions include in-depth studies on OV formation mechanisms, performance under complex conditions, and advanced sensor development, supported by theoretical calculations to better understand their effects on MoO3's electronic and adsorption properties.