Abstract
Bi4Ti3O12 square plates were synthesized via a hydrothermal route, and their growth process was systematically investigated. Carbon quantum dots (CQDs) were prepared using glucose as the carbon source, which were then assembled on the surface of Bi4Ti3O12 square plates via a hydrothermal route with the aim of enhancing the photocatalytic performance. XRD (X-ray powder diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), UV-vis DRS (diffuse reflectance spectroscopy), XPS (X-ray photoelectron spectroscopy), FTIR (Fourier transform infrared spectroscopy), PL (photoluminescence) spectroscopy, EIS (electrochemical impedance spectroscopy) and photocurrent spectroscopy were used to systematically characterize the as-prepared samples. It is demonstrated that the decoration of CQDs on Bi4Ti3O12 plates leads to an increased visible light absorption, slightly increased bandgap, increased photocurrent density, decreased charge-transfer resistance, and decreased PL intensity. Simulated sunlight and visible light were separately used as a light source to evaluate the photocatalytic activity of the samples toward the degradation of RhB in aqueous solution. Under both simulated sunlight and visible light irradiation, CQDs@Bi4Ti3O12 composites with an appropriate amount of CQDs exhibit obviously enhanced photocatalytic performance. However, the decoration of excessive CQDs gives rise to a decrease in the photocatalytic activity. The enhanced photocatalytic activity of CQDs-modified Bi4Ti3O12 can be attributed to the following reasons: (1) The electron transfer between Bi4Ti3O12 and CQDs promotes an efficient separation of photogenerated electron/hole pairs in Bi4Ti3O12; (2) the up-conversion photoluminescence emitted from CQDs could induce the generation of additional electron/hole pairs in Bi4Ti3O12; and (3) the photoexcited electrons in CQDs could participate in the photocatalytic reactions.
Highlights
To date, water pollution caused by organic dyes and pigments generated from chemical industries is getting increasingly serious and poses a great threat to aquatic life and human health
0.004 mol (1.9402 g) of Bi(NO3)3·5H2O was dissolved in 20 mL of 10% v/v dilute nitric acid solution, 0.003 mol (0.5691 g) of TiCl4 was dissolved in 20 mL of deionized water, and 0.2 mol (8 g) of NaOH was dissolved in 40 mL of deionized water
After the autoclave was naturally cooled to room temperature, the produced precipitate was collected by centrifugation, washed several times with deionized water and absolute ethanol, and dried at 60 ◦C for 12 h
Summary
Water pollution caused by organic dyes and pigments generated from chemical industries is getting increasingly serious and poses a great threat to aquatic life and human health. In the context of energy shortage, how to use solar energy as the power source to deal with water pollution has become an important subject To achieve this aim, recently, semiconductor-based photocatalysis has aroused tremendous interest [1,2,3,4,5,6]. Titanium dioxide and titanium-based oxide semiconductors have been extensively studied as an important class of semiconductor photocatalysts These semiconductor photocatalysts generally have a wide bandgap (Eg) greater than 3.0 eV and are photocatalytically active only under ultraviolet (UV) irradiation. As an important titanium-based oxide semiconductor, bismuth titanate (Bi4Ti3O12) has been extensively studied owing to its pronounced photocatalytic activity toward the degradation of organic pollutants and water splitting into hydrogen [33,34,35,36,37]. The characteristics, photocatalytic performance and photocatalytic mechanism of the as-prepared CQDs/Bi4Ti3O12 composites were systematically investigated and discussed
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