Abstract
Herein, a cobalt oxide/tungsten oxide (Co3O4/WO3) p–n heterojunction for NOx detection is developed and optimized. Field‐emission scanning electron microscopy shows that the WO3 nanorods are embellished with Co3O4 nanostructure. X‐ray photoelectron spectroscopy reveals the presence of oxygen vacancy on the Co3O4 coupled with WO3 heterojunction. Compared to bare WO3 and pure Co3O4, the Co3O4/WO3 heterojunction sensor shows significant sensitivity to NOx at 200 °C. The sensor exhibits higher linearity from 0.4 to 10 ppm of NOx, with a sensing response of 4.4–93%. The NOx sensitivity of the Co3O4/WO3 heterojunction sensor is ninefold higher than that of the pure WO3 sensor. Even in a high humidity (84%) environment, the Co3O4/WO3 heterojunction sensor demonstrates high NOx sensitivity. The sensor maintains remarkable stability measured for up to 4 weeks. The possible NOx sensing mechanism of the Co3O4/WO3 heterojunction is additionally discussed.
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