Coral-like α-Fe2O3 nanosensor for enhanced ammonia sensing at low operating temperature

Abstract

In this study, coral-like α-Fe₂O₃ gas sensing materials were synthesized via a simple hydrothermal-annealing method. By optimizing the calcination temperature, the material with high specific surface area and rapid dynamic response was obtained. The coral-like α-Fe₂O₃ which was calcined at 600 °C for 2 h exhibited excellent ammonia sensing properties: a low optimal operating temperature (220 °C), a high response value (50.26 to 200 ppm NH₃) alongside fast response/recovery times (13.6/33.4 s), and a good linear relationship between sensor response and ammonia concentration in the range of 10–200 ppm (regression coefficient R² = 0.987). The coral-like interconnected porous architecture significantly enhanced gas diffusion and increased the contact area between target gases and the sensing materials. Simultaneously, it facilitated adsorption/desorption processes on both internal and external surfaces, contributing to rapid response/recovery kinetics and high sensitivity. Furthermore, gas sensors based on coral-like α-Fe₂O₃ demonstrated excellent selectivity to ammonia and robust long-term stability. Finally, the gas sensing mechanism of ammonia detection was also discussed.