ZIF-derived porous ZnO-Co3O4 hollow polyhedrons heterostructure with highly enhanced ethanol detection performance

Porous transitional metal oxides hollow polyhedrons with controlled components have attracted tremendous attention due to their widespread applications. In this paper, novel porous ZnO-decorated Co3O4 hollow polyhedrons were synthesized by thermal decomposition of zeolitic imidazolate frameworks (ZIF-67) as self-sacrificial templates at 300 °C. Experimental results reveal that the porous 2 mol% ZnO-Co3O4 hollow polyhedrons present excellent response value of 106, short response/recovery time of 7/236 s to 1000 ppm ethanol at the optimal temperature of 200 °C, much higher than that of pure Co3O4 porous hollow polyhedrons (response value of only 5.39, response/recovery time of 9/323 s). Additionally, the 2 mol% ZnO-Co3O4 manifests a low detection limit of 1 ppm ethanol with a high response value of 1.57 and an applausive selectivity toward ethanol as compared to NH3, H2, CH4, CO2 and CH3COCH3. The enhanced gas sensing performance can be attributed to the formation of p-n heterojunction between Co3O4 and ZnO, as well as the porous hollow nanostructure with high porosity, large specific surface area, and remarkable capabilities of adsorbing oxygen. Our work offers a new avenue to employ ZIF-67 as templates for the fabrication of other hollow metal oxides with well-defined structures. More importantly, it demonstrates a great potential for the application of porous ZnO-Co3O4 hollow polyhedrons heterostructure to detect other gases.