MIL-68 derived In2O3 microtubes and Co3O4/In2O3 heterostructures for high sensitive formaldehyde gas sensors

The gas sensors with high response and selectivity are important for detecting and monitoring formaldehyde gas in real-time. In this paper, In2O3 microtubes are derived from metal organic framework named MIL-68 and Co3O4 nanoparticles are successfully loaded on the surface of In2O3 microtubes to form Co3O4/In2O3 heterostructures via one-step hydrothermal and calcination methods. The crystal structure, surface morphology and components of all samples are characterized and the formaldehyde gas-sensing performance is investigated in detail. All results indicates that Co3O4 nanoparticles greatly improve the formaldehyde gas-sensing performance of Co3O4/In2O3 heterostructures. Specifically, Co3O4/In2O3 (9 wt%) sensor exhibits a higher response (1215.47) to 10 ppm formaldehyde gas, which is about 10.16 times than that of pristine In2O3 sensor. Furthermore, Co3O4/In2O3 (9 wt%) sensor possesses a shorter recovery time (81 s), lower working temperature (190 °C), excellent selectivity, superior linear properties. As a result, Co3O4/In2O3 sensors exhibit excellent gas-sensing properties because of the synergistic effect of the catalytic activity of Co3O4 nanoparticles, the formation of p-n heterojunction and the increasing surface oxygen.