Humidity independent hydrogen sulfide sensing response achieved with monolayer film of CuO nanosheets

Detection of ppm and sub-ppm level airborne hydrogen sulfide (H₂S) is critical to both environmental monitoring and medical diagnosis. However, conductometric gas sensors based on semiconducting metal oxides are usually susceptible to humidity interference, which limits their performance in those applications. Typically, the hydroxyl groups formed by the chemisorption of water vapor on the surfaces of metal oxides prevent any further redox reaction, and in turn, passivate the sensing material. Departing from the traditional strategy of alleviating humidity interference with moisture adsorbents, we propose to explore the possible surface reactions between H₂S and hydroxyl groups on the surface of copper (II) oxide (CuO) in this work. With a monolayer film of CuO nanosheets, we observe an unprecedented humidity independent H₂S sensing performance. In addition, the sensor also shows excellent sensitivity and selectivity to H₂S and high stability in dry and wet conditions. The mechanism underlying the stable sensing response regardless of humidity variations is investigated with X-ray photoelectron spectroscopy.