Preparation of n-ZnO/p-Co3O4 heterojunctions from zeolitic imidazolate frameworks (ZIF-8/ZIF-67) for sensing low ethanol concentrations

Nano-heterojunctions of n-ZnO/p-Co3O4 with varying molar ratios of Co3O4 derived from a zeolitic imidazolate framework (ZIF-8/ZIF-67) were efficiently synthesized and well-characterized. The heterojunction-based gas sensors were then used for sensing various gases, including ethanol. Owing in part to the ZIF-8/ZIF-67 structure, the calcined n-ZnO/p-Co3O4 with 30 mol% Co3O4 was the best sensor, in-terms of high response, outstanding selectivity, and good repeatability for low concentrations of ethanol at 300 °C. According to detailed analysis, the high ethanol-sensing performance of the n-ZnO/p-Co3O4 nanocomposite could be attributed to the high-porosity of sensing materials, formation of p-n heterojunction at interfaces, the catalytic ability of Co3O4, and the high crystallinity of the ZnO phase in the nano-heterojunctions.