Co3O4–SnO2 nanobox sensor with a PN junction and semiconductor–conductor transformation for high selectivity and sensitivity detection of H2S

Abstract

Uniform Co₃O₄–SnO₂ nanoboxes have been synthesized successfully by a facile annealing treatment. Their hollow and cubic structure can be retained successfully during calcination. Due to their hollow structure and PN junction, these Co₃O₄–SnO₂ nanobox sensors can detect H₂S with high sensitivity at a low temperature of 180 °C. In addition, it was found that the Co₃O₄–SnO₂ nanobox sensors obtained at a higher annealing temperature displayed a higher sensitivity and lower recovery time to H₂S in a temperature range of 500 to 700 °C. X-ray photoelectron spectroscopy (XPS) was employed to confirm that the changes in resistance and the high sensitivities of the sensors are significantly attributable to the transformation of Co₃O₄ to CoS_x with high conductivity under an H₂S atmosphere.