Switching Effect of p-CuO Nanotube/n-In2S3 Nanosheet Heterostructures for High-Performance Room-Temperature H2S Sensing

High operating temperature and low response restrict the application of H₂S sensors. Due to the strong chemical affinity of CuO to H₂S and the large band gap and high stability of β-In₂S₃, CuO nanotube/In₂S₃ nanosheet p/n heterostructures have been delicately designed for binder-free gas sensors by a facile method consisting of sputtering, chemical etching, and annealing. A switching effect of H₂S concentration on the response of CuO/In₂S₃ gas sensors has been observed. When exposed to low-concentration H₂S (1-10 ppm), the response is less than 0.10 and dominated by the surface-type adsorption-desorption process between CuO and H₂S. When exposed to high-concentration H₂S, the sensor exhibits a superior response of 3511 toward 50 ppm H₂S, considerable selectivity, and long-term stability at room temperature. This dramatically enhanced response can be explained by the transformed junction from the CuO/In₂S₃ heterojunction to the CuS/In₂S₃ Schottky junction. These results suggest that the binder-free ceramic tube-type CuO/In₂S₃ gas sensor with considerable performance will have promising potential for H₂S gas detection. Moreover, this method provides an effective strategy to fabricate other binder-free gas sensors.