Enhanced NO2 gas sensing performance by hierarchical CuO–Co3O4 spheres

Composite sensing materials with complex hierarchical structures exhibit better performance in chemiresistive sensors due to rich defects induced by the hierarchical structures. Herein, the hierarchical spheres assembled by CuO-Co3O4 nanowires were successfully prepared via the hydrothermal and sintering procedure. SEM, TEM, and XRD results revealed that the hierarchical structure was controllably constructed by adjusting the composition of the CuO and Co3O4. XPS confirmed that the hierarchical structure could promote the enrichment of lattice oxygen. The CuO-Co3O4 composite with hierarchical structure-based sensor demonstrates enhanced NO2 sensing performance. The detection range of the sensor is from 200 ppb to 100 ppm. For interfering gases such as CO, H2S, NH3, ethanol, toluene, and xylene, the sensor shows good selectivity. At the optimal operating temperature of 160 oC, the sensor response is 37.86% to 10 ppm NO2. At the same time, the sensor shows good response and recovery characteristics, with response and recovery time of 158 s and 738 s respectively. These enhanced sensing performances should be attributed to rich lattice oxygen with chemical activity induced by the hierarchical structure. The route of structure-induced lattice oxygen to improve sensing performance could provide some new ideas for the synthesis of high-performance composite sensing materials. • Hierarchical spheres assembled by CuO-Co3O4 nanowires were prepared. • CuO-Co3O4 composite sensor has good selectivity and low detection limit (200 • ppb). • Structure-induced lattice oxygen can improve sensing performance.