Highly selective, low-temperature NH3 sensor based on spherical CuO and influence of its oxygen vacancy in sensing

Abstract

With the advent of the smart era, resistive semiconductor sensors present great promise for constructing sensing networks to deploy the Internet of Things for collecting air quality information. With the advent of the smart era, resistive semiconductor sensors present great promise for constructing sensing networks to deploy the Internet of Things for collecting air quality information. Oxygen vacancies affect the electronic structure of materials and give rise to unique physicochemical properties, which profoundly affect the sensing performance of the sensor. Peculiar phenomena and mechanisms of CuO oxygen vacancies have rarely been reported in gas sensitization. In this work, the oxygen vacancy-rich porous spherical CuO is prepared by thermal solvent reduction method. Moreover, the effect of oxygen vacancies is investigated on the electronic structure and electrical properties of CuO. Moreover, the sensing mechanism of oxygen vacancy with ammonia gas is explained by X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). The gas sensing results show that the response (631 %) of the synthesized oxygen vacancy-rich CuO-triethylene glycol (CuO-T) sensor to 100 ppm ammonia is 8.4 times higher than that of CuO-water (CuO-W) with a lower detection limit of 0.5 ppm at 200℃. The response of CuO-T sensor to ammonia gas is at least 19 times that of other gases, and has good humidity immunity. The designed CuO-T sensor has promising industrial applications. Meanwhile, the insightful understanding of CuO oxygen vacancies on electronic structure and electrical properties contributes to the design of high-performance ammonia sensors.