Dual sensitization of three-dimensional ordered macroporous Co3O4 thin films with Pt/Rh for enhanced NO2 detection

Abstract

Metal oxide semiconductor (MOS) gas sensors currently still suffer from a challenge to achieve high response in humid environment. In this work, a gas sensor based on porous Co3O4 thin films decorated by dual Pt/Rh catalysts is demonstrated for efficient NO2 detection with high humidity-resistivity. The porous Co3O4 thin films with three-dimensional ordered microstructure are synthesized by sacrificial template method. The loading of Pt/Rh catalysts by atom layer deposition (ALD) not only improve the detection sensitivity but also improve the moisture resistance of the sensor. ALD of Pt is proved to have a crucial effect on the sensor response. The Co3O4/Pt sensor with optimized Pt loading exhibits a response of 9.74–10 ppm NO2 at 145 °C, which is nearly 5 times higher than that (2.04) of pristine Co3O4 sensor. Further ALD of Rh on Co3O4/Pt enables the sensor to have a stable response even under 90% relative humidity. With optimized ALD Pt (15 cycles) and Rh (10 cycles), the sensor can well detect 0.5–10 ppm NO2 with fast response/recovery speed, as well as a low detection limit of 49 ppb. The strategy reported herein will pave the way to the development of new sensing materials and devices.