Achieving One Part Per Billion Hydrogen Sulfide (H₂S) Level Detection through Optimizing Composition and Crystallinity of Gold-Decorated Tungsten Trioxide (Au-WO₃) Nanofibers

As a common environmental pollutant and an important breath biomarker for several diseases, it is essential to develop a hydrogen sulfide gas sensor with a low-ppb level detection limit to prevent harmful gas exposure and allow early diagnoses of diseases in low-resource settings. Gold doped/decorated tungsten trioxide (Au-WO₃) nanofibers with various compositions and crystallinities were synthesized to optimize H₂S-sensing performance. Systematically experimental results demonstrated the ability to detect 1 ppb H₂S with a response value (R_air/R_gas) of 2.01 using a 5 at % Au-WO₃ nanofibers with average grain sizes of around 15 nm. Additionally, energy barrier difference of sensing materials in air and nitrogen (ΔE_b) and power law exponent (n) were determined to be 0.36 eV and 0.7, respectively, at 450 °C indicating that O^- is predominately ionic oxygen species and adsorption of O^- significantly altered the Schottky barrier between the grain. Such quantitative analysis provides a comprehensive understanding of H₂S detection mechanism.