Role of potassium loading in ZnO-based gas sensors under NO2 exposure – Operando diffuse reflectance infrared Fourier transform spectroscopic study

First published: 2025-04-28

Last Edited: 2025-04-28

Number of edits: 1

Unloaded, 0.08 and 0.9 at% potassium (K)-loaded ZnO gas sensors were investigated using operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy combined with simultaneous direct current (DC) sensor resistance measurements. At 250 °C in humidified (10%) synthetic air, during NO2 exposure, K-loaded ZnO exhibits a resistance decrease, which is contrary to the usual response of unloaded ZnO. Using DRIFTS, it was observed that for K-loaded ZnO, under NO2 exposure, free nitrates (such as KNO3) are formed and surface oxygen is removed, which explains the observed decrease in resistance. Moreover, the presence of K-related carbonates was confirmed through X-ray photoelectron spectroscopy. In addition, decomposition of monodentate carbonates was observed during the formation of free nitrates. To the best of our knowledge, this is the first time the peculiar sensor response of K-loaded ZnO to NO2 is reported and explained.

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