Highly sensitive and selective NO2 gas sensor fabricated from Cu2O-CuO microflowers

Three-dimensional (3D) hierarchical Cu2O-CuO microflowers assembled by nanorods were successfully obtained through an environmentally friendly hydrothermal route. Compared with other gases, the Cu2O-CuO microflowers-2 sensor had excellent selectivity, repeatability and long-term stability to NO2 at 187 °C. Moreover, during dynamic gas sensing measurement, the Cu2O-CuO microflowers-2 sensor showed the highest gas sensitivity (5–100 ppb), fast response time (35 s) and recovery time (47 s) to NO2, even under relatively high humidity. Significantly, at the optimal working temperature, the detection limit of the sensor was 5 ppb. The excellent sensing properties can be attributed to its unique structural advantages, more surface adsorbed oxygen, and the synergistic influence between the two-phase coexistence. •Cu2O-CuO microflowers were synthesized via a facile one-step hydrothermal method.•Cu2O-CuO microflowers-2 sensor exhibited better NO2 gas sensing property.•Cu2O-CuO microflowers-2 gas sensor had a low detection lower limit (5 ppb-1.37).•The response and recovery time of sensor is 35 and 47 s to 100 ppb NO2, respectively.