Synthesis of Co-Doped In2O3 Hierarchical Porous Nanocubes for High-Performance Hydrogen Sulfide Sensors

Abstract

Recently, because of the urgent need for safety and health protection, there has been a growing focus on exploring effective and feasible gas sensors based on metal oxide semiconductors (MOSs) for detecting trace levels of hydrogen sulfide (H₂S). In this context, a cobalt (Co) doping strategy was proposed to improve the H₂S-sensitive properties of In₂O₃ nanomaterials, enabling them to monitor 1 ppm of H₂S at a relatively lower temperature. The Co-doped In₂O₃ hierarchical porous nanocubes (Co–In₂O₃ HPNCs) were prepared through a hydrothermal route using In(OH)₃ as a precursor. When utilized as a sensing material to detect H₂S, the Co–In₂O₃ HPNCs demonstrated significant enhancements compared to pure In₂O₃. These enhancements include a reduction in the operating temperature (260 vs 300 °C), a significant increase in response (36.99 vs 12.28 for 20 ppm of H₂S), and better selectivity (13.21 vs 3.07 times to ethanol). Even to 1 ppm of H₂S, the Co–In₂O₃ sensor can give a response value of 1.86, highlighting its substantial potential for detecting H₂S at the limit of detection (LOD) of 1 ppm. A detailed analysis of the multiple sensitization effects of Co doping reveals that these improved H₂S sensing characteristics of Co–In₂O₃ HPNCs can be primarily traced back to three factors, namely, an increased oxygen vacancy concentration, a narrowing of the bandgap, and an upward shift of the Fermi level.