Low-temperature H₂S detection using Fe-doped SnO₂/rGO nanocomposite sensor

A low-temperature H₂S gas sensor was designed using 3% Fe-doped SnO₂/rGO nanocomposite as the sensing material. Fe-doped SnO₂ quantum dots (QDs) were prepared using a sol-gel combustion method, subsequently leading to the formation of the Fe-SnO₂/rGO nanocomposite through a simple sonication process. To evaluate the performance of the sensor material, the sample underwent comprehensive characterization using XRD, FE-SEM, HRTEM, Raman shift, XPS and BET surface area analysis based on nitrogen (N₂) adsorption-desorption. The XRD pattern HR-TEM confirmed the formation of a well-defined tetragonal crystal phase of SnO₂, indicating high structural integrity. Meanwhile, the BET analysis revealed a specific surface area of 72.7 m² g^-1 with pore size of 7.83 nm. Morphological analysis (HR-TEM) revealed that 3% Fe-doped SnO₂ QDs was uniformly dispersed on the rGO surface, with an average particle size of 5.6 nm. Gas sensing performance of pristine SnO₂ (S1), 3% Fe-doped SnO₂ QDs (S2), and 3% Fe-SnO₂/rGO (S3) nanocomposite based sensors was evaluated at operating temperatures ranging from 25 °C to 175 °C. Incorporation of rGO significantly enhanced the sensitivity of the 3% Fe-doped SnO₂/rGO nanocomposite towards H₂S compared to pristine SnO₂ and 3% Fe-SnO₂ QDs. The 3% Fe-SnO₂/rGO (S3) based sensor demonstrated a significant response of about 42.4 to 10 ppm H₂S at a low operating temperature of 100 °C, with a rapid response time of 21 seconds. It also exhibited excellent selectivity for H₂S against interfering gases such as NH₃, LPG, and CO. The enhanced sensitivity and selectivity are attributed to the synergistic interaction between 3% Fe-SnO₂ and rGO. A possible gas sensing mechanism underlying the improved performance of the nanocomposite is discussed.