Construction of hierarchical ZnO flower-like structure for boost H2S detection at low temperature

Novel flower-like ZnO nanomaterials were synthesized by a simple solvothermal method without using any template and surfactant combined with subsequent calcination. The resultant ZnO flowers displayed a hierarchical structure with diameters of 1.4–1.6 µm, consisting of overlapped nanorods grew radially from the center of the ZnO flowers. The gas sensors based on such ZnO flowers were highly sensitive to H2S gas in terms of a high response (157.3) and excellent selectivity towards 100 ppm H2S at the low operating temperature of 92 °C, accompanied with the detection limit of 0.05 ppm. The superior gas-sensing capabilities might benefit from the porous hierarchical architecture, which could facilitate the rapid adsorption of gas molecules and enhance the consequent charge transfer. Furthermore, the surface state of the ZnO flowers before and after exposure to H2S gas at 92 °C were investigated through the XPS technique and a possible H2S sensing mechanism over ZnO was proposed.