Abstract: The development of gas sensors capable of detecting nitrogen dioxide (NO₂) with exceptional selectivity and sensitivity remains a significant challenge at low or room temperatures (RT), particularly for automotive exhaust, where traditional gas sensors frequently exhibit limitations. To address this issue, we have designed a novel binary metal oxide RT NO₂ sensor based on In₆WO₁₂ by utilizing the synergistic effects of electron scattering and space charge transfer between grains. Especially, the mesoporous In₆WO₁₂ nanosphere assembled from nanoparticles of ∼8 nm was developed through an ethylenediamine-assisted coprecipitation strategy, offering a large surface area and multiple diffusion paths. Additionally, the loading of Pr₂O₃ significantly improves the NO₂ sensing properties by modulating the reaction process of NO₂ and decreasing the work function. RT NO₂ sensing experiments demonstrated that the In₆WO₁₂/Pr₂O₃ (IWO-5) sensor exhibited an impressive response (90), rapid response/recovery speed (108 s/148 s), an ultra-low limit of detection (20 ppb), and outstanding selectivity (the K value was up to 69.8). The In-situ DRIFTS and energy band structure analyses further prove the importance of absorbed oxygen in the NO₂ sensing process, caused by the loading of Pr₂O₃, decreasing the work function. This work introduces a new option for gas-sensing materials, emphasizing the significance of adsorbed oxygen in the NO₂ gas-sensing mechanism and offering a novel approach for designing RT gas sensors.

Key words: In₆WO₁₂/Pr₂O₃, Gas sensor, Space charge transfer, Surface reaction, Electron scattering