Synthesis of a Flower-Like g-C₃N₄/ZnO Hierarchical Structure with Improved CH₄ Sensing Properties

In this paper, a hierarchical structure of graphite carbon nitride (g-C₃N₄) modified ZnO (g-C₃N₄/ZnO) was synthesized using a simple precipitation-calcination method. Through this method, g-C₃N₄ nanosheets with a controlled content were successfully decorated on the petals of flower-like ZnO. Various techniques were used to confirm the successful formation of the g-C₃N₄/ZnO hierarchical structure. The methane (CH₄) sensing properties of g-C₃N₄/ZnO sensor were investigated. The result exhibited that after decorating ZnO with g-C₃N₄, the CH₄ sensing performances of the fabricated sensor were remarkably improved. At the optimum operating temperature of 320 °C, the response of the sensor fabricated with CNZ-3 (the sample with an optimum content of g-C₃N₄) towards 1000 ppm CH₄ was as high as 11.9 (R_a/R_g), which was about 2.2 times higher than that of the pure ZnO sensor (5.3). In addition, the CNZ-3 sensor also exhibited a fast response/recovery speed (15/28 s) and outstanding long-term stability. The enhancing CH₄ sensing mechanism may be contributed to enlarged surface area, pore structure, and g-C₃N₄-ZnO n-n junction.