Probing Lattice‐Oxygen Redox in Pt‐WO 3 Nanocrystals by Operando Spectroscopy: Bridging Surface Chemistry and Ethanol Sensing

Understanding how lattice oxygen participates in gas sensing remains a challenge in metal‐oxide chemistry. Here, we combine operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), operando Raman spectroscopy, ex situ electron paramagnetic resonance (EPR), in situ X‐ray diffraction, electrical measurements, and density functional theory (DFT) calculations to elucidate the ethanol‐sensing mechanism of Pt‐loaded WO 3 nanocrystals. Among the compositions, 1Pt‐WO 3 exhibits the highest ethanol response (S = 98.8 at 350°C), sixfold higher than pristine WO 3 . Reversible changes in the W–O vibrational region, together with an EtOH‐induced EPR signal at g = 2.007 and DRIFTS results, support the formation of reduced W species and oxygen‐vacancies during ethanol exposure and reoxidation of reduced W species and oxygen vacancy healing by O 2 . In situ XRD showed no bulk phase transformation, consistent with a redox process occurring at the surface or near‐surface region. Under oxygen‐containing atmospheres, vacancy healing restores lattice integrity and stabilizes sensor performance. Pt acts as a catalytic mediator that facilitates O 2 activation and promotes oxidation of partial‐oxidation intermediates toward CO 2 , thereby amplifying sensor response. These results establish a near‐surface lattice‐oxygen redox cycle as a key mechanistic feature of ethanol sensing and provide a basis for the design of high‐performance metal‐oxide gas sensors.