Enhanced room-temperature NO2 sensing performance of mulberry-like Cu2O/CuO composites

Realizing room-temperature detection to low concentrations of hazardous gases can not only contribute to the long-term stability and low power consumption of gas sensors, but also benefit the life and health of human being. In this work, we firstly fabricated mulberry-like Cu2O/CuO composites by one-pot hydrothermal method. The optimized Cu2O/CuO nanocomposite exhibits the outstanding room-temperature sensitivity to NO2, such as the higher response, shorter response & recovery time, and lower detection threshold. Specifically, the room-temperature responses (AR/Ra) arrive at 19.3%, 62.3%, 70.9% and 82.0% to 0.01, 0.1, 1 and 10 ppm NO2, and the response & recovery time are 58 and 250 s while employing 0.1 ppm NO2, respectively. Furthermore, the optimized Cu2O/CuO composite presents excellent selectivity and reproducibility, good long-term stability to NO2, and non-monotone humidity dependence of response. Specifically, the fluctuations of response are less than 1.5% to 0.1-1 ppm NO2 after five cycles, and-2% and 3% to 0.1 and 0.5 ppm NO2 for 30 consecutive days, respectively. Finally, the gas sensing mechanism is also proposed based on the microstructure and micro-chemistry of the optimized Cu2O/CuO composite, the redox reactions on the surface, and the formation of p-p heterojunction. This work provides a promising candidate material for room-temperature detection of NO2.