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0D/2D Z-scheme Heterojunctions of Bismuth Tantalate Quantum Dots/Ultrathin g-C3N4 Nanosheets for Highly Efficient Visible Light Photocatalytic Degradation of Antibiotics Kai Wang, Gaoke Zhang, Jun Li, Yuan Li, and Xiaoyong Wu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b14275 • Publication Date (Web): 27 Nov 2017 Downloaded from http://pubs.acs.org on November 30, 2017
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ACS Applied Materials & Interfaces
0D/2D
Z-scheme
Tantalate
Heterojunctions of
Quantum
Dots/Ultrathin
Bismuth g-C3N4
Nanosheets for Highly Efficient Visible Light Photocatalytic Degradation of Antibiotics Kai Wang a, Gaoke Zhang a,b* , Jun Li a, Yuan Li a ,Xiaoyong Wu a* a
Hubei Key Laboratory of Mineral Resources Processing and Environment, School of Resources
and Environmental Engineering, Wuhan University of Technology, 122 Luoshi Road, Wuhan 430070, China b
State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology,
Wuhan 430070, China
KEYWORDS: bismuth tantalate; quantum dots; g-C3N4 nanosheets; Z-scheme photocatalyst; antibiotics.
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ABSTRACT
Constructing 0D/2D Z-scheme photocatalysts is a great promising path to improve photocatalytic activity by efficient enhancing charge separation. Herein, we fabricated a visible-light responsive Bi3TaO7 quantum dots (QDs)/g-C3N4 nanosheets (NSs) 0D/2D Z-scheme composite via a facile ultrasound method and Bi3TaO7 QDs could be interspersed on the surface of g-C3N4 NSs uniformly. Furthermore, the strong interaction between Bi3TaO7 QDs and g-C3N4 NSs disturbed the CN heterocycles by forming C=O bonds between C atoms of the N-(C)3 group and O atoms of the Ta-O bond. The optimum composite with 20 wt% g-C3N4 NSs showed the superior photocatalytic activity for degradation of ciprofloxacin (CIP) over the composites prepared by mechanical mixing and solid-state methods, the photocatalytic efficiency of which were 4 and 12.2 times higher than those of bare Bi3TaO7 and g-C3N4. Photoluminescence (PL), timeresolved transient PL decay spectra and photocurrent together verify that the photogenerated hole-electron pairs in this 0D/2D Z scheme composite have been effectively separated. The enhanced photocatalytic activity of as-synthesized photocatalysts could be attributed to the synergistic effect of efficient Z-scheme charge separation, highly dispersed 0D Bi3TaO7 nanocrystals, coordinating sites of 2D g-C3N4 NSs and the strong coupling between them. This study might pave the way toward designing novel visible -light induced 0D/2D photocatalyst systems for highly efficient degradation of antibiotics.
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1. INTRODUCTION Nowadays, antibiotics, as one of the widely used products and applications of drugs, have brought increasing effect into the natural environment and human health.1,2 However, these antibiotics cannot be efficiently decomposed by traditional wastewater treatment methods due to the inhibition of the proliferation of bacteria. Hence, it is imperative to remove antibiotics effectively from the wastewater with the aid of environmental-friendly techniques.3,4 Semiconductor photocatalysis is a promising way to decompose the antibiotics in aqueous solution, owing to its high efficiency, low-cost and high stability in wastewater treatment. Although some semiconductor photocatalysts have recently been developed for photocatalytic antibiotics degradation,5-7 the visible light induced photocatalysts with high activity are still strongly required. Among various photocatalysts, bismuth-based materials have become one of promising photocatalysts because of their efficient utilization of visible light.8 Typically, because of an incommensurately modulated structure, high chemical stability and suitable band gap (2.7eV), bismuth tantalate (Bi3TaO7) has attracted considerable interest as a candidate for a proper photocatalyst for pollutant degradation. For instance, Luo et al. synthesized a novel Ag0/Bi3TaO7 plasmonic catalyst, which exhibited the enhanced photocatalytic performance for the antibiotic degradation.9 Our group10 also synthesized superior photocatalytic property of nanometer-size Bi3TaO7 by a low-cost sol–gel method. Thus, it probably has great potential as an attractive photocatalyst for the removal of antibiotics through the photochemical pathway. Nevertheless, its extended application was still extensively limited to the high recombination rate of electron-hole
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pairs. Consequently, it is necessary to make some attempts to ameliorate the photocatalytic activity of the Bi3TaO7 by enhancing charge separation significantly. As we all know, the design and fabrication of Z-scheme photocatalysts present admirable advantages over charge separation. Moreover, in comparison of heterostructure, Z-scheme structure can also keep enhanced reduction ability of the semiconductor with higher conduction band position and boosting oxidation ability of the semiconductor with lower valence band position in composite. Under this consideration, Z- scheme g-C3N4/Bi3TaO7 composites have been synthesized by solid-state reaction method.11 The separation ability of photogenerated holeelectron pairs has been enhanced to some extent. While it still has some space to further improve photocatalytic activity by optimizing morphology and the photocatalysts coupling in composites, which are essential factors for building a high efficiency of Z-scheme composite. Recently, construction of closely coupled 0D/2D composites has been found to be a great potential way to form a novel heterojunction with excellent performance of photocatalysis.12-15 Firstly, 0D semiconductor photocatalysts have peculiar advantages over other dimensional particles owing to their small size (
