Sc and Au co-modification in In2O3 nanofiber gas sensors: A critical strategy for ultrasensitive and practical H2S detection

The development of sensing materials capable of detecting H 2 S with ultrasensitivity and practicability is essential. To address this need, an Au and Sc co-modification strategy was proposed to boost the gas-sensing sensitivity of In 2 O 3 to H 2 S. In 2 O 3 and a sequence of binary (Au-In 2 O 3 and Sc x In (2-x) O 3 ) and ternary (Au-Sc x In (2-x) O 3 ) nanofibers (NFs) with different compositions were fabricated by electrospinning-calcination. Morphology characteristics revealed that the doping of Sc led to a reduction in the grain size, whereas the modification of Au induced an increase in the surface roughness of the NFs. Notably, after evolving pristine In 2 O 3 to the co-modified composites, the sensors exhibited an appreciable increase in sensitivity to H 2 S (from 0.51/ppm to 4.41/ppm), and ultralow detection limit of 5 ppb (measured) and 0.82 ppb (calculated). Moreover, the optimal Au-Sc x In (2-x) O 3 sensor exhibited preferable practicability, including selectivity (selectivity coefficient > 7), repeatability (RSD < 0.95 %, n  = 7), stability (response decreased 4.3 % over 30 days), and moisture resistance (decreased 15 % at 88 % RH). Ultraviolet photo-electron spectroscopy and UV–vis spectroscopy analysis revealed that the enhanced performance was attributed to the formation of Au-Sc x In (2-x) O 3 heterojunctions, the electronic and chemical sensitization effect of Au, and the synergistic effect between Sc and Au.