Novel ZnO/CdO heterostructure for high efficiency formaldehyde sensing with high response and low detection limit at low temperature

Abstract

ZnO/CdO heterostructure nanocomposites were synthesized using a simple stirring method at room temperature combined with subsequent calcination. The ZnO/CdO nanocomposites-based sensors displayed higher selectivity and higher response at lower optimal operation temperature to formaldehyde gas than pure ZnO and CdO. Especially, the sensor based on the ZnO/CdO prepared with 0.2 g CdSO4 (ZnO/CdO-3 sensor) showed a response value of 104 to 50 ppm HCHO at 150 °C, which is around 5.9 times that of the pristine ZnO sensor. In addition, the ZnO/CdO-3 sensor showed a low experimental detection limit of 100 ppb and relatively good humidity resistance. Moreover, the sensor can work at even lower working temperature with high response, for example, the response is 7.5 to 50 ppm HCHO at 90 °C. The doping of CdO and the synergistic effect of the n-n heterojunction at the interface are the main reasons contributing to the improvement of HCHO sensing property.