A multiscale perspective on the surface functional properties of nanostructured metal-oxide gas sensors

Chemoresistive gas sensing is intrinsically multiscale, with macroscopic device performance emerging from molecular surface reactions coupled to charge transport across nanostructured networks. However, the causal relationships linking surface chemistry to device-level response remain poorly defined, limiting predictive sensor design. Here, we establish a multiscale, operando framework that correlates surface functional chemistry with the electrical response of WO3-based sensors for D-limonene detection. By integrating temperature-dependent electrical measurements with NH3-TPD, FT-IR spectroscopy using 2,6-dimethylpyridine, and operando DRIFTS under realistic operating conditions, we resolve structure–property–function relationships that are typically inaccessible using conventional ex situ approaches. Surface acidity emerges as a decisive functional descriptor: optimal sensing performance coincides with the highest density of acidic sites within a characteristic operating temperature window. Coordinatively unsaturated W6+ centers are identified as active sites for CQC bond activation in D-limonene, enabling pronounced sensor responses at a relatively low temperature of 200 1C. Operando DRIFTS further reveals the direct participation of surface hydroxyl groups in the sensing reaction, while moderate humidity does not alter the dominant reaction pathway, underscoring the robustness of the mechanism under realistic conditions. By explicitly linking surface Lewis acidity and hydroxyl chemistry to macroscopic sensing behaviour, this work advances chemoresistive gas sensing as a mechanism-driven, predictive discipline. More broadly, the multiscale operando strategy introduced here provides a generalizable blueprint for the rational design of functional metal-oxide interfaces.