Construction of NiO@ZnSnO₃ hierarchical microspheres decorated with NiO nanosheets for formaldehyde sensing

The composite of ZnSnO₃ hierarchical microspheres decorated with NiO nanosheets have been synthesized by a facile solution-based chemical precipitation at 85 °C followed by self-assembly and annealing, which is low-cost and high-yield. The structure, morphology, composition and specific surface of composite were characterized by XRD, SEM, TG, XPS and BET analysis, respectively. The gas sensing experiments show that the sensor based on composite of NiO/ZnSnO₃ mole ratio of 1:10 not only exhibits high response of 2.2 and 10.4 to 0.1 and 1 ppm formaldehyde, respectively and good selectivity to some of reducing gases, but also has low detection limit and rapid response and recovery at operating temperature of 85 °C. The mechanism of composite enhancing gas sensing was also discussed in detail, which can be ascribed to the large specific surface area of composite and the formation of p-n heterojunctions at the interface between NiO and ZnSnO₃.