Controllable construction of Cr2O3-ZnO hierarchical heterostructures and their formaldehyde gas sensing properties

The designed Cr2O3-ZnO hierarchical heterostructures have been successfully synthesized by a facile two-step route. The SEM, TEM, XRD and EDS mapping characterizations demonstrate that Cr2O3 nanoparticles are well decorated on surfaces of nanosheet-assembled flowerlike ZnO, constructing three dimensional Cr2O3-ZnO hierarchical heterostructures. Such hierarchical architectures are developed and applied in formaldehyde (HCHO) gas detection. The gas sensing results indicate that Cr2O3-ZnO heterostructures based sensors exhibit superior HCHO gas sensing properties with rapid response/recovery behavior (1 s/5 s) toward 100 ppm formaldehyde (HCHO) gas, and favorable stability and repeatability with the on/off phenomenon when switching between HCHO and air at a optimal working temperature of 220 °C. The superior formaldehyde gas sensing performances are predominantly attributed to the appropriate sensitization effect induced by Cr2O3 nanoparticles and the special three dimensional hierarchical architectures.