Synergistic oxygen plasma and variable-valence metal (Ni/Mn) doping strategy engineering enhanced low-temperature H2S sensing mechanism in In2O3 nanotubes

Hydrogen sulfide (H 2 S), as a highly toxic gas, poses severe threats to human health when its concentration exceeds safety thresholds. Therefore, it is crucial to develop H 2 S sensors with high response, excellent selectivity and fast response characteristics. In this work, we successfully synthesized In 2 O 3 -based nanotubes through a synergistic strategy combining variable-valence metal ion doping (Ni, Mn) and oxygen plasma treatment, achieving ultra-sensitive H 2 S detection at a low operating temperature of 75°C. Remarkably, the oxygen plasma-treated Ni-doped In 2 O 3 nanotubes (denoted as Ni-In 2 O 3 -plasma) exhibited outstanding sensing performance to 5 H 2 S gas: An unprecedented response value of 6601.4, a low detection limit of 100 ppb and superior anti-interference selectivity. Moreover, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) proves the possible products in the gas-sensing reactions. Mechanistic investigations through electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) revealed that the enhanced performance is mainly attributed to the two synergistic effects of abundant oxygen vacancies and high Ni 3 + /Ni 2⁺ ratio in the composite materials. This study provides an efficient and controllable optimization strategy for the development of high-performance metal oxide semiconductor (MOS)-based H 2 S sensors.