Abstract
Impurity element doping is extensively taken as one of the most efficient strategies to regulate the electronic structure as well as the rate of photogenerated charge separation of photocatalysts. Herein, a one-pot hydrothermal synthesis process was exploited to obtain La-doped ZnIn2S4 microspheres, aiming at gaining insight into the role that doping ions played in the improvement of pollutant photodegradation. Systematical characterization means, comprising of X–ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis) diffuse reflection spectroscopy and Raman spectra, combination with high-resolution transmission electron microscopy (HRTEM), were employed to in depth reveal the concomitancy of La ions and ZnIn2S4 crystal lattice. The results showed that the La-doped ZnIn2S4 samples exhibited a slightly wider and stronger spectral absorption than pristine ZnIn2S4; and the specific surface area of doped ZnIn2S4 samples was a bit larger. The La-doped ZnIn2S4 electrodes showed improved photocurrent response, and the photocurrent density reached a maximum value at La content of 1.5 wt%. As expected, La-doped ZnIn2S4 samples exhibited a remarkable enhancement of photocatalytic behaviour toward the photodegradation of tetracycline hydrochloride (TCH) and methyl orange (MO). The prominently enhanced photoactivity of doped ZnIn2S4 samples was due to the synergistic effect of the elevated visible-light absorption ability and effective photogenerated charge carriers’ separation.
Highlights
As we are stepping into 21st century with rapid development of economic and manufacturing, more and more organic pollutants, such as dyes and tetracycline hydrochloride (TCH), from the textile industry or pharmaceutical industry, will be increasingly discharged into waste water
The results showed that the introduction of Cr, Fe, and Co supressed the photocatalytic behaviour for hydrogen evolution, while the hydrogen evolution rate of a Mo-doped ZIS sample was larger than that of pure ZIS [29]
The investigation of surface components and chemical status was realized by the utilization of the X-ray photoelectron spectrometer (XPS, ESCALAB 250Xi, Thermo Fisher Scientific corporation, New York, NY, USA), and the 284.6 eV of C1s was taken as the criterion to correct binding energies of other elements
Summary
As we are stepping into 21st century with rapid development of economic and manufacturing, more and more organic pollutants, such as dyes and tetracycline hydrochloride (TCH), from the textile industry or pharmaceutical industry, will be increasingly discharged into waste water. Besides the aforementioned work on metal ions, Xie et al designed and developed O-doped ZIS nanosheets with novel structure, acting as a platform to improve the photocatalytic activity due to the increased density of states and accelerated separation rate of photoexcited carriers [33]. These findings in previous studies are interesting and impressive, they inspire us to pursue for other effective doping in ZIS photocatalyst with improved photo-reactivity toward organic pollutant degradation. As far as we know, this study is the first report about the synthesis and improved photocatalytic performance of La-doped ZIS
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