Achieving Room-Temperature ppb-Level H₂S Detection in a Au-SnO₂ Sensor with Low Voltage Enhancement Effect

Although semiconductor metal oxide-based sensors are promising for gas sensing, low-power and room temperature operation (24 ± 1 °C) remains desirable for practical applications particularly considering the request of energy saving or net zero emission. In this study, we demonstrate a Au/SnO₂-based ultrasensitive H₂S gas sensor with a limit of detection (LOD) of 2 ppb, operating at very low voltages (0.05 to 0.5 V) at room temperature. The Au/SnO₂-based sensor showed approximately 7 times higher response (the ratio of change in the current to initial current) of ∼270% and 4 times faster recovery (126 s) compared to the pure SnO₂-based sensor when exposed to 500 ppb H₂S gas concentration at 0.5 V operating voltage at relative humidity (RH) 17.5 ± 2.5%. The enhancement can be attributed to the catalytic characteristics of AuNPs, increasing the number of adsorbed oxygen species on sensing material surfaces. Additionally, AuNPs aid in forming flower-petal-like Au/SnO₂ nanostructures, offering a larger surface area and more active sites for H₂S sensing. Moreover, at low voltage (<1 V), the localized dipoles at the Au/SnO₂ interface may further enhance the absorption of polar oxygen molecules and hence promote the reaction between H₂S and oxygen species. This low-power, ultrasensitive H₂S sensor outperforms high-powered alternatives, making it ideal for environmental, food safety, and healthcare applications.