Nanolevel control of gas sensing characteristics via p-n heterojunction between Rh₂O₃ clusters and WO₃ crystallites

Today semiconducting metal oxide (SMOX) based gas sensors are used in a wide array of applications. Dopants, e.g., rhodium, are often used to change the sensor response of SMOXs. The adjustment of sensing characteristics with dopants is usually done empirically, and there is a knowledge gap surrounding how the presence of dopants alters the chemistry of sensing. Here using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), dc resistance measurements, and operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, it was understood how surface loading with Rh₂O₃ changes sensing with WO₃. As a result of uniform surface loading, reactions between the Rh₂O₃ clusters and the analyte gas dominate the reception. Changes in the p-n heterojunction between Rh₂O₃ and WO₃ are responsible for the transduction. These results in combination with existing literature indicate that, through controlled surface doping, it is possible to intentionally tune the sensor characteristics of SMOXs.