Modeling Interfacial Interaction between Gas Molecules and Semiconductor Metal Oxides: A New View Angle on Gas Sensing

Abstract

With the development of internet of things and artificial intelligence electronics, metal oxide semiconductor (MOS)-based sensing materials have attracted increasing attention from both fundamental research and practical applications. MOS materials possess intrinsic physicochemical properties, tunable compositions, and electronic structure, and are particularly suitable for integration and miniaturization in developing chemiresistive gas sensors. During sensing processes, the dynamic gas-solid interface interactions play crucial roles in improving sensors' performance, and most studies emphasize the gas-MOS chemical reactions. Herein, from a new view angle focusing more on physical gas-solid interactions during gas sensing, basic theory overview and latest progress for the dynamic process of gas molecules including adsorption, desorption, and diffusion, are systematically summarized and elucidated. The unique electronic sensing mechanisms are also discussed from various aspects including molecular interaction models, gas diffusion mechanism, and interfacial reaction behaviors, where structure-activity relationship and diffusion behavior are overviewed in detail. Especially, the surface adsorption-desorption dynamics are discussed and evaluated, and their potential effects on sensing performance are elucidated from the gas-solid interfacial regulation perspective. Finally, the prospect for further research directions in improving gas dynamic processes in MOS gas sensors is discussed, aiming to supplement the approaches for the development of high-performance MOS gas sensors.

Metal and Metal Oxide Supported on Ordered Mesoporous Carbon as Heterogeneous Catalysts

“…When the relative size of pore diameter is much larger than the mean free path of the guest molecule (λ), the collision occurs among reactant molecules during the molecular movement. This is described by bulk molecular diffusion in the macropores . The proportion of the collision between the molecules and the macropore walls is very small, resulting in the reactant being inaccessible to the active sites.…”

“…The coefficient of Knudsen diffusion is expressed as D normalK = 2 3 r 8 R T / π M , where r is the average pore radius and M is the intrinsic molecular parameter . Knudsen diffusion mainly occurs in the mesopores for large reactant molecules . The collision frequency is the important pre-exponential factor in the Arrhenius equation, which represents the frequency of collisions between reactant molecules at a standard concentration.…”

“…This value is used to determine the activation entropy (Δ S 0* ) for a reaction. Knudsen diffusion in mesopores that boosts the collision may greatly increase the reaction rate . But the studies are limited.…”

“…This is described by bulk molecular diffusion in the macropores. 133 The proportion of the collision between the molecules and the macropore walls is very small, resulting in the reactant being inaccessible to the active sites.…”

Polymerization-Induced Aggregation Approach toward Uniform Pd Nanoparticle-Decorated Mesoporous SiO2/WO3 Microspheres for Hydrogen Sensing

“…The working principle of SMOs gas sensors is based on their chemiresistance features, that is, the resistance of SMOs can change rapidly upon contact with guest molecules followed by gas adsorption and catalytic reaction. − In the last decade, various SMOs such as ZnO, − SnO 2 , − MoO 3 , − In 2 O 3 , − and WO 3 , have been extensively explored as sensitive materials for gas sensors toward hydrogen. Among various SMOs, WO 3 -based composites have been considered an ideal sensing material with great potential for applications because they have the advantages of a wide band gap (2.6–3.0 eV), , tunable redox property, and good stability .…”