Solid-State Method Synthesis of SnO₂-Decorated g-C₃N₄ Nanocomposites with Enhanced Gas-Sensing Property to Ethanol

Abstract

SnO₂/graphitic carbon nitride (g-C₃N₄) composites were synthesized via a facile solid-state method by using SnCl₄·5H₂O and urea as the precursor. The structure and morphology of the as-synthesized composites were characterized by the techniques of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), thermogravimetry-differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), and N₂ sorption. The results indicated that the composites possessed a two-dimensional (2-D) structure, and the SnO₂ nanoparticles were highly dispersed on the surface of the g-C₃N₄ nanosheets. The gas-sensing performance of the samples to ethanol was tested, and the SnO₂/g-C₃N₄ nanocomposite-based sensor exhibited admirable properties. The response value (Ra/Rg) of the SnO₂/g-C₃N₄ nanocomposite with 10 wt % 2-D g-C₃N₄ content-based sensor to 500 ppm of ethanol was 550 at 300 °C. However, the response value of pure SnO₂ was only 320. The high surface area of SnO₂/g-C₃N₄-10 (140 m²·g^-1) and the interaction between 2-D g-C₃N₄ and SnO₂ could strongly affect the gas-sensing property.

Keywords: 2-D graphitic carbon nitride; SnO2; ethanol; gas-sensing performance; nanocomposite.

Figure 1

The appearance diagram (a) and the internal structure diagram (b) of the CGS-4TPS gas-sensing test system, and the structure of the gas sensor substrate (c).

Figure 2

X-ray diffraction (XRD) patterns of the graphitic carbon nitride (g-C₃N₄), SnO₂, and SnO₂/g-C₃N₄ nanocomposites with different g-C₃N₄ contents.

Figure 3

X-ray photoelectron spectroscopy (XPS) survey of g-C₃N₄, SnO₂, and SnO₂/g-C₃N₄-10 samples: (a) the general scan spectrum; (b) Sn 3d spectrum; (c) O 1s spectrum; (d) C 1s spectrum; and (e) N 1s spectrum.

Figure 4

Thermogravimetry–differential thermal analysis (TG–DTA) profiles of g-C₃N₄.

Figure 5

Scanning electron microscope (SEM) images of (a) g-C₃N₄; (b) SnO₂; and (c) SnO₂/g-C₃N₄-10 samples.

Figure 6

Energy dispersive spectrometer (EDS) spectra (a) and SEM image (b) of the SnO₂/g-C₃N₄-10 nanocomposite, and EDS mappings of the Sn (c), O (d), C (e), and N (f) element related to (b).

Figure 6

Energy dispersive spectrometer (EDS) spectra (a) and SEM image (b) of the SnO₂/g-C₃N₄-10 nanocomposite, and EDS mappings of the Sn (c), O (d), C (e), and N (f) element related to (b).

Figure 7

Transmission electron microscopy (TEM) images of (a) g-C₃N₄; (b) SnO₂; and (c) SnO₂/g-C₃N₄-10; and (d) HRTEM image of the SnO₂/g-C₃N₄-10 composite.

Figure 8

(a) N₂ adsorption–desorption isotherms and (b) the corresponding pore size distribution curves of the g-C₃N₄, SnO₂, and SnO₂/g-C₃N₄-10 samples. The dV/dD value was shifted by 0.05 and 0.1 units for the curves of data sets SnO₂/g-C₃N₄-10 and SnO₂, respectively.

Figure 9

(a) Response values of the sensors based on SnO₂, SnO₂/g-C₃N₄-7, SnO₂/g-C₃N₄-10, and SnO₂/g-C₃N₄-13 to 500 ppm of ethanol as a function of operating temperature; (b,c) the responses of sensors (SnO₂, SnO₂/g-C₃N₄-7, SnO₂/g-C₃N₄-10, and SnO₂/g-C₃N₄-13) operated at 300 °C versus different concentrations of ethanol.

Figure 10

(a) Real-time response curves of pure SnO₂ and SnO₂/g-C₃N₄-10 to ethanol in the range of 500–2000 ppm, and (b) response–recovery curve of SnO₂/g-C₃N₄-10 to 2000 ppm of ethanol.

Figure 11

(a) Repeatability and (b) stability measurements of the SnO₂/g-C₃N₄-10 sensors to 500 ppm of ethanol at 300 °C.

Figure 12

Responses of SnO₂ and SnO₂/g-C₃N₄-10-based sensors to 500 ppm of different reducing gases at 300 °C.

Figure 13

Schematic diagram of test gas reaction with the as-prepared nanocomposite.