Surface functionalization of Co3O4 hollow spheres with ZnO nanoparticles for modulating sensing properties of formaldehyde

The Co3O4 hollow spheres with 3D hierarchical structure have been synthesized successfully by a facile precipitation method using SiO2 spheres as hard template. The hierarchical structure of Co3O4 as a good substrate material can be further functioned because of its stable and porous structure as well as large specific surface. To improve the gas sensing properties of Co3O4, ZnO nanoparticles were introduced to modify Co3O4 into the Co3O4/ZnO composites. The structure and properties of composite were characterized by XRD, FESEM, HRTEM and XPS analysis. Gas-sensing experiments reveal that the hollow Co3O4/ZnO composite not only exhibits high sensitivity that is 4 times higher than that of pristine Co3O4, rapid response and recovery but also has excellent selectivity and relatively low operating temperature to 10 ppm HCHO. Such excellent performance may be attributed to the hollow hierarchical structure and the formation of p-n heterojunctions at interface between both oxides.