Chemical bath deposition fabrication of flower-like Co3O4-NiO/ZnO array for ppb-level CO sensor

Carbon monoxide is a colorless and odorless, highly toxic gas, posing a significant risk to both human health and industrial safety. Zinc oxide has garnered significant interest for its outstanding chemical stability and cost-effectiveness in the development of CO sensors. However, sensors based on a single ZnO has the shortcomings of low sensitivity and high detection limit, rendering them challenging to meet the precise detection requirements for CO. To address this issue, ZnO nanoflower arrays were prepared by chemical bath deposition (CBD), followed by modification of varying ratios of Co 3 O 4 and NiO onto the ZnO nanoflower arrays. The response value of the sensor based on Co 3 O 4 -NiO/ZnO-2 to 100 ppm CO was 104% at 310 °C. Remarkably, the sensor achieved an exceptionally low detection limit of 1 ppb. Further, the crystal structure and morphology characteristics of Co 3 O 4 -NiO/ZnO were systematically analyzed by XRD, SEM, TEM, XPS, Raman, EDS, EPR, and BET. The results show that the improvement in gas-sensing performance is mainly ascribed to the ZnO nanoflower array and the heterojunctions formed among Co 3 O 4 , NiO and ZnO. In this study, Co 3 O 4 and NiO decorated ZnO nanoflower arrays were prepared by a two-step CBD, offering a novel approach for advancing high-performance CO sensors.