Highly Selective Room Temperature Detection of NH3 and NOx Using Oxygen-Deficient W18O49-Supported WS2 Heterojunctions

In this paper, we reported the controlled synthesis of tungsten disulfide/reduced tungsten oxide (WS2/W18O49) heterojunctions for highly efficient room temperature NOx and ammonia (NH3) sensors. X-ray diffraction analysis revealed the formation of the oxygen-deficient W18O49 phase along with WS2. Field-emission scanning electron microscopy and transmission electron microscopy displayed the formation of WS2 flakes over W18O49 nanorods. X-ray photoelectron spectroscopy showed the presence of tungsten in W4+, W5+, and W6+ oxidation states corresponding to WS2 and W18O49, respectively. The WS2/W18O49 heterojunction sensor exhibited sub-ppm level sensitivity to NOx and NH3 at room temperature. The heterojunction sensor detected 0.6 ppm NOx and 0.5 ppm NH3, with a corresponding response of 7.1 and 3.8%, respectively. The limit of detection of the sensor was calculated to be 0.05 and 0.17 ppm for NH3 and NOx, respectively. The cyclic stability test showed that the sensor exhibited high stability even after 24 cycles for the detection of NH3 and 14 cycles for NOx. Compared to pristine WO3 and WS2, the WS2/ W18O49 heterojunction showed high selectivity toward NOx and NH3. The results could be useful for the development of room temperature NOx and NH3 sensors.

Automated summary

In this study, tungsten disulfide/reduced tungsten oxide (WS2/W18O49) heterojunctions were synthesized and used as highly efficient room temperature NOx and ammonia (NH3) sensors. The heterojunction sensors exhibited sub-ppm level sensitivity to NOx and NH3, and showed high stability even after multiple cycles of detection. The WS2/W18O49 heterojunction also demonstrated high selectivity towards NOx and NH3 compared to pristine WO3 and WS2.