Synthesis of Co₃O₄/Ta₂O₅ heterostructure hollow nanospheres for enhanced room temperature ethanol gas sensor

Designing and constructing heterostrucutres is the trend of enhancing sensing performance of metal oxide semiconductor based gas sensors. A new kind of porous Co₃O₄/Ta₂O₅ heterostructure hollow nanospheres was successfully synthesized by the assistance of carbon colloidal nanospheres and following annealing. The Ta₂O₅ nanostructures with ultrathin hollow spherical shell (∼5 nm) were attached with numerous Co₃O₄ nanoparticles, forming heterojunction in the contact surface. The Ta₂O₅ hollow spheres act as the supporting model, hindering the aggregation of Co₃O₄ nanoparticles and possessing more specific surface area. For room temperature (25 °C) gas sensing application, the Co₃O₄/Ta₂O₅ hollow nanospheres exhibited outstanding ethanol detecting properties. The gas response toward 10, 20, 50, and 100 ppm of ethanol achieved 20%, 50%, 90% and 180%, respectively. The Co₃O₄/Ta₂O₅ hollow nanospheres also exhibited outstanding selectively and reliable stability, which can be attributed to the formation of the heterojunction in the contact surface of Co₃O₄ and Ta₂O₅, leading to the extension of electron depletion layer. - Highlights: • A new kinds of mesoporous Co₃O₄/Ta₂O₅ heterostructure hollow nanospheres. • Co₃O₄/Ta₂O₅ exhibits outstanding ethanol detecting performance at room temperature. • The ethanol sensitivity of Co₃O₄/Ta₂O₅ is three times that of pure Co₃O₄. • The excellent sensitivity is due to the special structure of Co₃O₄/Ta₂O₅.