Ultrafast Response/Recovery and High Selectivity of the H2S Gas Sensor Based on α-Fe2O3 Nano-Ellipsoids from One-Step Hydrothermal Synthesis.

Ultrafast response/recovery and high selectivity of gas sensors are critical for real-time and online monitoring of hazardous gases. In this work, α-Fe2O3 nano-ellipsoids were synthesized using a facile one-step hydrothermal method and investigated as highly sensitive H2S-sensing materials. The nano-ellipsoids have an average long-axis diameter of 275 nm and an average short-axis diameter of 125 nm. H2S gas sensors fabricated using the α-Fe2O3 nano-ellipsoids showed excellent H2S-sensing performance at an optimum working temperature of 260 °C. The response and recovery times were 0.8 s/2.2 s for H2S gas with a concentration of 50 ppm, which are much faster than those of H2S gas sensors reported in the literature. The α-Fe2O3 nano-ellipsoid-based sensors also showed high selectivity to H2S compared to other commonly investigated gases including NH3, CO, NO2, H2, CH2Cl2, and ethanol. In addition, the sensors exhibited high-response values to different concentrations of H2S with a detection limit as low as 100 ppb, as well as excellent repeatability and long-term stability.