Abstract
Graphitic carbon nitride (g-C3N4) nanosheets with a thickness of only a few nanometres were obtained by a facile deammoniation treatment of bulk g-C3N4 and were further hybridized with Bi2WO6 nanoparticles on the surface via a solvothermal method. The composite photocatalysts were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis diffuse reflection spectroscopy and X-ray photoelectron spectroscopy (XPS). The HR-TEM results show that the nano-sized Bi2WO6 particles were finely distributed on g-C3N4 sheet surface, which forms heterojunction structure. The UV–vis diffuse reflectance spectra (DRS) show that the absorption edge of composite photocatalysts shifts towards lower energy region in comparison with those of pure g-C3N4 and Bi2WO6. The degradation of methyl orange (MO) tests reveals that the optimum activity of 8 : 2 g-C3N4-Bi2WO6 photocatalyst is almost 2.7 and 8.5 times higher than those of individual g-C3N4 and Bi2WO6. Moreover, the recycle experiments depict high stability of the composite photocatalysts. Through the study of the influencing factors, a possible photocatalytic mechanism is proposed. The enhancement in both photocatalytic performance and stability was caused by the synergistic effect, including the effective separation of the photogenerated electron-hole pairs at the interface of g-C3N4 and Bi2WO6, the smaller the particle size and the relatively larger specific surface area of the composite photocatalyst.
Highlights
Semiconductor photocatalysts have drawn much attention in the past decades because they represent a promising technology to use natural sunlight energy to promote chemical reactions, such as watersplitting, pollutant degradation and organic transformation [1,2]
The photocatalytic activity of the catalysts was tested by degrading the methyl orange (MO) solution under a visible light using a 500 W xenon lamp with a 420 nm cut-off filter as the light source
This phenomenon can be ascribed to two aspects: one is that the (002) of g-C3N4 and (131) of Bi2WO6 diffraction peaks were located in a similar position, (002)
Summary
Semiconductor photocatalysts have drawn much attention in the past decades because they represent a promising technology to use natural sunlight energy to promote chemical reactions, such as watersplitting, pollutant degradation and organic transformation [1,2]. The traditional photocatalysts are active only in the UV region and have high electron-hole recombination rates, which led to its inability to make full use of solar energy and reduce the photocatalytic performance [4]. Owing to the larger specific surface area and well-matched band structures, the activity of the obtained composed catalysts was significantly high than those of the pure Bi2WO6 and g-C3N4 respectively. These composed catalysts were very stable and could be used multiple times, retaining a relatively high photocatalytic activity. Through the analysis of the capture experiment, the possible photocatalytic mechanism was put forward
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