Preparation of g-C₃N₄/SnO₂ nanocomposites and their gas-sensing properties

g-C₃N₄/SnO₂ nanocomposites were prepared by hydrothermal method. The microstructure and crystal phase of the samples were analyzed by X-ray diffraction, transmission electron microscopy, and N₂ adsorption–desorption analysis. The results showed that SnO₂ nanoparticles which are rutile tetragonal structure and dispersed on the surface of g-C₃N₄ nanosheets. The g-C₃N₄ doping enlarged the specific surface area of the composites as well as decreased the crystallite size of SnO₂. Compared with pure SnO₂, the gas-sensing properties of the composites were enhanced. The sensor based on SnO₂ doped with 3 wt% g-C₃N₄ showed good gas-sensing properties to formaldehyde, and the response was 506.4 to 100 ppm formaldehyde at 100 ℃, which was 4.8 times than the pure SnO₂ sensor. It also exhibited good selectivity to formaldehyde at 100 ℃. Additionally, the response (S = 39.6) of the sensor based on 5 wt% g-C₃N₄-doped SnO₂ was twice than the pure SnO₂ sensor to 100 ppm acetone.