Highly efficient ethanol vapour detection using g-C₃N₄/ZnO micro flower-like heterostructural composites

This work proposes precursor pyrolysis, ultrasonic exfoliation and hydrothermal methods as well as high-temperature calcination strategies to fabricate heterostructured g-C₃N₄/ZnO composites with excellent ethanol vapour sensing properties. The structure, composition and morphology of the as-prepared g-C₃N₄/ZnO composites were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Then, the sensing properties of the g-C₃N₄/ZnO composites for ethanol (C₂H₅OH) were studied, and g-C₃N₄ doping with different mass ratios was used to control the gas-sensing properties of the composites. Compared with pure ZnO and g-C₃N₄, the performance of g-C₃N₄ with 1% doping content is the best, and the gas sensing activity of the 1% g-C₃N₄/ZnO composite is greatly improved at the optimal working temperature (280 °C). The response to 100 ppm ethanol reaches 81.4, which is 3.7 times that of the pure ZnO-based sensor under the same conditions. In addition, the sensor has good selectivity as well as fast response and recovery speeds (24 s and 63 s, respectively). Finally, a reasonable gas sensing enhancement mechanism is proposed, and it is believed that the constructed g-C₃N₄/ZnO micro flower-like heterostructure and the distinct positions of the valence and conduction bands of ZnO and g-C₃N₄ lead to the obtained sensor exhibiting a large specific surface area and increased conductivity, thereby improving the g-C₃N₄/ZnO-based sensor sensing performance.