Carbon derived hollow α-Fe2O3 nanochains via high-efficiency microwave-assisted synthesis for excellent formaldehyde detection

Formaldehyde (HCHO) is widely used in manufacturing processes, contributing to its release and buildup as an indoor air pollutant. Timely detection of HCHO is crucial to prevent its severe toxic effects. To enhance the gas-sensing capability toward HCHO, porous α-Fe₂O₃ hollow nanochains were successfully synthesized using a microwave-assisted method with carbon nanochains as a template. Various characterization techniques and calculation analysis were used to investigate its sensing performance and explore its underlying mechanism. The results revealed that the α-Fe₂O₃ hollow nanochains, with a large specific surface area of 65.69 m² g⁻¹, are constructed from sub-level α-Fe₂O₃ nanoparticles in the size range of 8–23 nm. The formation of this structure is primarily attributed to the hotspot effect induced by microwave radiation. The α-Fe₂O₃ sensor demonstrated superior sensitivity, excellent selectivity, swift response/recovery, and long-term stability in detecting 0.1–50 ppm HCHO vapor at 150 °C. Notably, it exhibited a high response of 122 with a response time of 78 s towards 10 ppm HCHO at 150 °C. The enhanced HCHO-sensing properties can be attributed to the unique structure of porous hollow nanochains with abundant oxygen vacancy defects. This research presents a promising, low-cost, and efficient approach for developing an effective α-Fe₂O₃ sensor for low-ppm HCHO detection.