NiO/ZnO composite decorated on rGO for detection of NO2

Abstract

A novel NO 2 sensor based on rGO (0.5 wt%)-NiO/32ZnO composite was successfully prepared by hydrothermal method and hydrazine hydrate reduction method. Compared with the ZnO, the rGO (0.5 wt%)-NiO/32ZnO composite has a significant improvement in the sensing performance of NO 2 , indicating the new rGO (0.5 wt%)-NiO/32ZnO composite with p-n heterojunction is a promising sensing material for the detection of NO 2 gases. • One-step hydrothermal method synthesized a novel gas sensing of NiO/ZnO composite. • The triadic composite exhibits high sensitivity, higher response and shorter response time to NO2. • The improvement is due to the formation of junction and the modification of rGO. The rGO-NiO/ZnO composites were successfully synthesized by hydrothermal and hydrazine hydrate reduction methods and were used to detect NO 2 . The structure and morphology of the composites were characterized using spectrum techniques. The sensing tests showed that the triadic composite of rGO (0.5 wt%)-NiO/32ZnO exhibits a liner response toward NO 2 in the concentration range of 0.5–3 ppm and the highest response reaches 75.3 to 2 ppm NO 2 at 140 °C, which is 4.55 times and 1.38 times higher than that of pure ZnO and binary composite of NiO/32ZnO, respectively. The composite also exhibits a fast response of 39 s and a low detection limit of 46 ppb. The improvement mechanism is ascribed to the formation of p-n heterojunction that benefits from the formation of an additional depletion layer at the junction interface and the decoration of rGO increases surface active sites and accelerates electron transfer.