Regulation of N-type In₂O₃ Content on the Conductivity Type of Co₃O₄ Based Acetone Sensor

A double-jet electrospinning method was adopted to fabricate In₂O₃/Co₃O₄ nanofibers (NFs). The sensitivity of In₂O₃/Co₃O₄ NFs and In₂O₃ NFs were compared and analyzed, and the morphology, structure, chemical composition, and gas-sensing properties of the samples were comprehensively characterized. The results show that the introduction of Co₃O₄ can improve the response of In₂O₃/Co₃O₄ to acetone, to 29.52 (In₂O₃/Co₃O₄) and 12.34 (In₂O₃) to 200 ppm acetone at 2000°C, respectively. In addition, the doping of Co₃O₄ was found to reduce the optimum working temperature of pure In₂O₃ from 275°C to 200°C. The composite of Co₃O₄ and In₂O₃ not only enhances the sensing performance, but also leads to a conversion of p-n conductivity type. The phenomenon of the p-n transition is relevant to operating temperature and proportion of In₂O₃ and Co₃O₄. While the enhanced acetone sensing properties of In₂O₃/Co₃O₄ NFs may be attributed to the p-n heterojunction between n-type In₂O₃ and p-type Co₃O₄ crystalline grains, which promotes the electron migration. The synergistic effects between In₂O₃ and Co₃O₄ and the large specific surface area of NFs additionally contribute to the improvements of acetone sensing performance.