Surface Enhancement Effects of Tiny SnO₂ Nanoparticle Modification on α-Fe₂O₃ for Room-Temperature NH₃ Sensing

The development of a gas sensor capable of detecting ammonia with high selectivity and rapid response at room temperature has consistently posed a formidable challenge. To address this issue, the present study utilized a one-step solvothermal method to co-assemble α-Fe₂O₃ and SnO₂ by evenly covering SnO₂ nanoparticles on the surface of α-Fe₂O₃. By controlling the morphology and Fe/Sn mole ratio of the composite, the as-prepared sample exhibits high-performance detection of NH₃. At room temperature conditions, a gas sensor composed of α-Fe₂O₃@3%SnO₂ demonstrates a rapid response time of 14 s and a notable sensitivity of 83.9% when detecting 100 ppm ammonia. Experiments and density functional theory (DFT) calculations suggest that the adsorption capacity of α-Fe₂O₃ to ammonia is enhanced by the surface effect provided by SnO₂. Meanwhile, the existence of SnO₂ tailors the pore structure and effective surface area of α-Fe₂O₃, creating multiple channels for the diffusion and adsorption of ammonia molecules. Additionally, an N-N heterostructure is formed between α-Fe₂O₃ and SnO₂, which enhances the potential energy barrier and improves the ammonia sensing performance. Demonstration experiments have proved that the sensor shows significant advantages over commercial sensors in the process of ammonia detection in agricultural facilities. This work provides new insights into the perspectives on ammonia detection at room temperature.