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Interface Oxygen Vacancy-Enhanced Co3O4/WO3 Nanorod Heterojunction for Sub-ppm Level Detection of NOx |
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| Authors: | Mathankumar Manoharan Kamaraj Govindharaj Karuppasamy Muthumalai Sabarish Kumaravel Yuvaraj Haldorai Ramasamy Thangavelu Rajendra Kumar |
| Affiliation: | 1. Advanced Materials and Devices Laboratory, Department of Nanoscience and Technology, Bharathiar University, Coimbatore, Tamilnadu, 641046 India;2. Advanced Materials and Devices Laboratory, Department of Nanoscience and Technology, Bharathiar University, Coimbatore, Tamilnadu, 641046 India School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeonbuk, 38541 Republic of Korea |
| 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. |
| Keywords: | gas sensors metal oxides nanostructures. NOx oxygen vacancy p–n heterojunctions |