Porous Cr 2 O 3 Architecture Assembled by Nano-Sized Cylinders/Ellipsoids for Enhanced Sensing to Trace H 2 S Gas.

How to achieve high sensing of Cr 2 O 3 -based sensors for harmful inorganic gases is still a challenge. To this end, Cr 2 O 3 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 Cr 2 O 3 -600), and also possesses multistage pore distribution for target gas accessibility. Interestingly, the synergism of two shapes of nanocrystals enables the Cr 2 O 3 -based sensor to realize highly sensitive detection of trace H 2 S gas. At 170 °C, Cr 2 O 3 -600 exhibits a high response of 42.8 to 100 ppm H 2 S gas, which is 3.45 times larger than that of Cr 2 O 3 -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 Cr 2 O 3 material. In addition, the Cr 2 O 3 -600 sensor shows satisfactory results for actual monitoring of the corruption process of fresh chicken.