High pressure torsion technology applied to ZnO nanomaterials for enhancing the room-temperature HCl sensing performance

Hydrogen chloride (HCl) gas is widely generated in industrial processes and poses significant risks to human health and ecosystems. Therefore, highly efficient and sensitive sensors are essential for its detection. Among existing HCl gas sensors, chemiresistive sensors based on metal oxide semiconductors (MOSs) have gained considerable interest owing to their structural simplicity, low cost, and ease of miniaturization. However, these sensors often suffer from limitations such as slow response, low selectivity, and high operating temperatures. In this study, we successfully synthesized gas-sensing materials enriched with crystal defects and bulk strain through high-pressure torsion (HPT) technology. These modifications provide additional active sites for gas adsorption and reaction, and induce crystal field distortion that tunes the electronic structure, ultimately enhancing the HCl sensing performance. The optimal sample, ZnO-300R 3/2 , exhibited a response value of 213.79 % toward 100 ppm HCl gas, which is 14.6 times higher than that of the pristine ZnO. Combining spectroscopic analysis with density functional theory (DFT) calculations, we clarified the synergistic mechanism between electronic band structure modulation and surface lattice oxygen activation. This work provides valuable insights for designing novel room-temperature gas sensors and promotes a deeper understanding of surface lattice oxygen-mediated sensing mechanisms.