Porous Cr₂O₃ Architecture Assembled by Nano-Sized Cylinders/Ellipsoids for Enhanced Sensing to Trace H₂S Gas

How to achieve high sensing of Cr₂O₃-based sensors for harmful inorganic gases is still a challenge. To this end, Cr₂O₃ nanomaterials assembled from different building blocks were simply prepared by chromium salt immersion and air calcination with waste scallion roots as the biomass template. The hierarchical architecture calcined at 600 °C is constructed from nanocylinders and nanoellipsoids (named as Cr₂O₃-600), and also possesses multistage pore distribution for target gas accessibility. Interestingly, the synergism of two shapes of nanocrystals enables the Cr₂O₃-based sensor to realize highly sensitive detection of trace H₂S gas. At 170 °C, Cr₂O₃-600 exhibits a high response of 42.8 to 100 ppm H₂S gas, which is 3.45 times larger than that of Cr₂O₃-500 assembled from nanocylinders. Meanwhile, this sensor has a low detection limit of 1.0 ppb (S = 1.4), good selectivity, stability, and moisture resistance. These results show that the combination of nanosized cylinders/ellipsoids together with exposed (104) facet can effectively improve the sensing performance of the p-type Cr₂O₃ material. In addition, the Cr₂O₃-600 sensor shows satisfactory results for actual monitoring of the corruption process of fresh chicken.