Regular ArticleRoom-temperature synthesis of carnation-like ZnO@AgI hierarchical nanostructures assembled by AgI nanoparticles-decorated ZnO nanosheets with enhanced visible light photocatalytic activity
Graphical abstract
Carnation flower-like ZnO@AgI hierarchical nanostructures assembled by AgI nanoparticles-decorated ZnO nanosheets with enhanced visible light photocatalytic activity.
Introduction
Environmental protection and remediation, especially waste water treatment has been attracting worldwide attention [1], [2], [3], [4]. A number of ways have been developed for the purification of wastewater and semiconductor-based heterogeneous photocatalysis has been proved to be a promising technique for the treatment of wastewater which is contaminated by organic pollutants [5], [6], [7], [8], [9], [10], [11], [12]. Among various semiconductors, TiO2 and ZnO have been widely studied and recognized to be preferable photocatalysts [2], [3], [4], [9], [13], [14], [15]. However, both TiO2 and ZnO have wide band gaps and can only absorb a small portion of solar light in the UV region [16]. Furthermore, a high recombination rate of the photogenerated electron-hole pairs also decreases the photocatalytic efficiency, for only a small amount of the charge carries can be transferred to the surface to conduct the photocatalytic reaction. One of the approaches to address these issues is to combine TiO2 and ZnO with narrow gap semiconductors, which not only can expand the light absorption to visible light region, but also can decrease the electron-hole recombination [17], [18].
Recently, a new type of visible-light-driven plasmonic photocatalyst, AgX@Ag (X = Cl, Br and I) has been developed and found to possess excellent photocatalytic activity under visible light irradiation due to the strong surface plasmon resonance effect of metallic Ag nanoparticles [19], [20], [21], [22], [23], [24], [25]. However, silver belongs to noble metals, it is of being rare and expensive, and thus the compounds of silver halides (AgX) are relatively expensive compared with ZnO and TiO2. The high cost of AgX photocatalyst hinders their practical application in large-scale photocatalytic processes. Consequently, preparation of AgX with low-cost semiconductors such as TiO2 and ZnO not only can extend the light response into visible light region but also cut down the cost in practical application. Over the past few years, much attention has focused on the coupling of TiO2 and ZnO with AgCl [26], [27], [28], [29], [30] and AgBr [31], [32], [33], [34], and rare attention has been paid to the fabrication and photocatalytic investigation of ZnO@AgI composites [35]. Vignesh and co-workers prepared ZnO@AgI composites by a multi-step method [36]. First, ZnO precursors were obtained by the reaction between ZnSO4·7H2O and NaHCO3. Then ZnO nanoparticles were prepared by calcining the ZnO precursors at 350 °C for 3 h. Finally, ZnO@AgI composite was fabricated by the deposition of AgI on the surface of ZnO by a precipitation method at room temperature for 12 h. Lu and co-workers prepared ZnO@AgI by immersing ZnO nanorod arrays into a mixed solution of AgNO3 and KI for 8 h. [37]. Recently, Shaker-Agjekandy and Habibi-Yangjeh fabricated ZnO@AgI composites by using an one-pot refluxing method at temperature of 96 °C [38] or a one-pot microwave-assisted methodology [35]. However, some of the reported synthesis procedures are multi-steps and time-consuming, and some need high temperature or special instrument. Therefore, to find a cost-effective and time-saving methodology for the preparation of ZnO@AgI composite is still of great importance.
In this study, carnation flower-like ZnO@AgI hierarchical nanostructures assembled by AgI nanoparticles-decorated ZnO nanosheets were successfully fabricated at room temperature without using any special instruments. First, carnation-like ZnO hierarchical nanostructures consist of ZnO nanosheets with thickness of about 25 nm were prepared using citrate as complex reagent. Then AgI nanoparticles with diameter of about 20 nm were decorated onto the surface of the ZnO nanosheet with the assistance of polyvinylpyrrolidone (PVP, K-30) and ethylene glycol. The AgI-decorated ZnO nanosheets were cross-linked and assembled into sphere-like nanostructures with lots of meso-pores and macro-pores. This unique hierarchical structure is beneficial for enlarging the accessible surface area, creating more photocatalytic active sites, facilitating the transfer of electrons, reducing the recombination of the photogenerated electron-hole pairs, and consequently leading to the enhanced photocatalytic performance.
Section snippets
Materials preparation
Carnation-like ZnO hierarchical nanostructures were prepared by the reaction of zinc acetate (Zn(CH3COO)2·2H2O) with sodium hydroxide (NaOH) in the presence of trisodium citrate (C6H5Na3O7·2H2O) [39]. All of the reagents were used as received without further purification. Deionized (DI) water was used in all experiments. In a typical synthesis, 3 mmol of zinc acetate and 5 mmol of trisodium citrate were dissolved into 50 mL DI water under magnetic stirring at room temperature, then 15 mmol of NaOH
Characterization
Fig. 1 shows the XRD patterns of ZnO, AgI and ZnO@AgI samples. The ZnO sample shows diffraction peaks at 2θ of 31.74°, 34.34°, 36.16°, 47.56°, 56.54°, 62.82°, 66.48°, 67.96°, 69.02° correspond well to the (100), (002), (101), (102), (110), (103), (200), (112) and (201) crystal planes of of ZnO (JCPDS No. 36-1451) with hexagonal wurtzite crystal structure (a = b = 3.250 Å, and c = 5.207 Å) [15]. The AgI sample shows diffraction peaks at 2θ of 22.36°, 23.68°, 25.36°, 32.94°, 39.22°, 42.66° and 46.28°,
Conclusions
In summary, ZnO@AgI composites were successfully prepared by a facile deposition-precipitation method at room temperature and characterized by XRD, SEM, DRS and XPS techniques. The photocatalytic activity of the composites was evaluated by the degradation of methyl orange under visible-light irradiation. The activity of the composites was first increased and then gradually decreased with increasing the mole fraction of AgI. The superior activity was observed for the ZnO@Ag-5% sample in which
Acknowledgement
This work was supported by the Innovation Training Project for University Students in the College of Chemistry and Chemical Engineering at China West Normal University (2015, H. Huang), the Open Project of Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province (CSPC2016-3-2), and the Innovation Team Project of the Education Department of Sichuan Province (15TD0018).
References (70)
- et al.
Photodegradation of phenol via C3N4-agar hybrid hydrogel 3D photocatalysts with free separation
Appl. Catal. B-Environ.
(2016) - et al.
Solar photocatalytic degradation of azo dye: comparison of photocatalytic efficiency of ZnO and TiO2
Sol. Energy Mater. Sol. Cell
(2003) - et al.
Photocatalytic removal of spiramycin from wastewater under visible light with N-doped TiO2 photocatalysts
Chem. Eng. J.
(2015) - et al.
Advanced photocatalytic performance of graphene-like BN modified BiOBr flower-like materials for the removal of pollutants and mechanism insight
Appl. Catal. B Environ.
(2016) - et al.
Ionic liquid-induced strategy for carbon quantum dots/BiOX (X = Br, Cl) hybrid nanosheets with superior visible light-driven photocatalysis
Appl. Catal. B Environ.
(2016) - et al.
Simultaneous synthesis-immobilization of Ag nanoparticles functionalized 2D g-C3N4 nanosheets with improved photocatalytic activity
J. Alloy. Compd.
(2017) - et al.
Efficient and sustainable metal-free GR/C3N4/CDots ternary heterostructrues for versatile visible-light-driven photoredox applications: toward synergistic interaction of carbon materials
Chem. Eng. J.
(2017) - et al.
Visible-light-active ZnO via oxygen vacancy manipulation for efficient formaldehyde photodegradation
Chem. Eng. J.
(2015) - et al.
Synthesis of g-C3N4/Ag3VO4 composites with enhanced photocatalytic activity under visible light irradiation
Chem. Eng. J.
(2015) - et al.
Photoelectrocatalytic degradation of phenol-containing wastewater by TiO2/g-C3N4 hybrid heterostructure thin film
Appl. Catal. B Environ.
(2017)
One-step pyrolytic synthesis of ZnO nanorods with enhanced photocatalytic activity and high photostability under visible light and UV light irradiation
J. Alloy. Compd.
Eosin Y-sensitized nitrogen-doped TiO2 for efficient visible light photocatalytic hydrogen evolution
J. Mol. Catal. A Chem.
Synthesis of CuO-ZnO nanophotocatalyst for visible light assisted degradation of a textile dye in aqueous solution
Chem. Eng. J.
Preparation of ZnO/Cu2O compound photocatalyst and application in treating organic dyes
J. Hazard. Mater.
Controllable synthesis of plasmonic Ag/AgBr photocatalysts by a facile one-pot solvothermal route
Chem. Eng. J.
One-pot synthesis of AgCl@Ag hybrid photocatalyst with high photocatalytic activity and photostability under visible light and sunlight irradiation
Chem. Eng. J.
Highly efficient visible light plasmonic photocatalysts Ag@Ag(Cl, Br) and Ag@AgCl-AgI
ChemCatChem
Ag/AgCl/ZnO nano-networks: preparation, characterization, mechanism and photocatalytic activity
J. Mole. Catal. A Chem.
Visible-light-driven photocatalytic properties of self assembled cauliflower-like AgCl/ZnO hierarchical nanostructures
J. Mol. Catal. A Chem.
Ag/AgCl modified self-doped TiO2 hollow sphere with enhanced visible light photocatalytic activity
J. Alloy. Compd.
Preparation of Ag-AgBr/TiO2-graphene and its visible light photocatalytic activity enhancement for the degradation of polyacrylamide
J. Alloy. Compd.
Synthesis of micro-nano heterostructure AgBr/ZnO composite for advanced visible light photocatalysis
Mater. Lett.
Simple and large scale one-pot method for preparation of AgBr-ZnO nanocomposites as highly efficient visible light photocatalyst
Appl. Surf. Sci.
Photocatalytic activity of AgI sensitized ZnO nanoparticles under visible light irradiation
Powder Technol.
Facile fabrication of highly efficient AgI/ZnO heterojunction and its application of methylene blue and rhodamine B solutions degradation under natural sunlight
Appl. Surf. Sci.
Facile one-pot method for preparation of AgI/ZnO nanocomposites as visible-light-driven photocatalysts with enhanced activities
Mater. Sci. Semicond. Process.
Rapid and simple synthesis of 3D ZnO microflowers at room temperature
Mater. Lett.
Quantum yields of active oxidative species formed on TiO2 photocatalyst
J. Photochem. Photobiol., A
Crystal structure of zinc citrate
J. Inorg. Biochem.
Controlled synthesis of heterostructured Ag@AgI/ZnS microspheres with enhanced photocatalytic activity and selective separation of methylene blue from mixture dyes
J. Taiwan Inst. Chem. Eng.
Synthesis of spindle-shaped AgI/TiO2 nanoparticles with enhanced photocatalytic performance
Appl. Surf. Sci.
Highly enhanced photocatalytic reduction of Cr(VI) on AgI/TiO2 under visible light irradiation: Influence of calcination temperature
J. Hazard. Mater.
Facile synthesis of Cu2O nanocube/polycarbazole composites and their high visible-light photocatalytic properties
J. Solid State Chem.
Solution synthesis of Cu2O/TiO2 core-shell nanocomposites
Colloids Surf. A
Adsorption removal of Congo red from aqueous solution by polyhedral Cu2O nanoparticles: kinetics, isotherms, thermodynamics and mechanism analysis
J. Alloy. Compd.
Cited by (57)
Enhanced photocatalytic activity of ZnO microflowers by a trace amount of Ti<inf>3</inf>C<inf>2</inf> MXene
2023, Inorganic Chemistry CommunicationsBi<inf>5</inf>O<inf>7</inf>I/BiOBr type-Ⅱ heterojunction broaden the light absorption range to achieve high photocatalytic activity
2023, Materials Science in Semiconductor ProcessingA novel green synthesis of Bi<inf>2</inf>WO<inf>6</inf>-based photocatalysts for efficient pollutants degradation using low-power UV-A LEDs
2022, Journal of Alloys and CompoundsCitation Excerpt :Moreover, RhB adsorbed on the BWO is photosensitized by light, conducing to an excited state of RhB (RhB+•, LUMO), transferring an e- to CB of BWO. In the CB, e- have the necessary ECB (0.16 eV) to interact with O2•-/O2 (0.28 eV), whereas h+ in VB possess high positive EVB (3.26 eV) to react with H2O and OH- producing high oxidant •OH species (•OH/OH− and •OH/H2O, +1.99 and +2.72 eV vs. NHE [30,54]), respectively), causing RhB degradation. The straightforward, green, and novel procedure followed for synthesizing BWO and Ag/BWO catalysts by the metathesis reaction between Bi(NO3)3 and Na2WO4 in an alkaline molten salt medium was successfully used to obtain highly efficient photocatalysts.
Ternary photocatalyst of ZIF-8 nanofilms coupled with AgI nanoparticles seamlessly on ZnO microrods for enhanced visible-light photocatalysis degradation
2022, Journal of the Taiwan Institute of Chemical EngineersCitation Excerpt :Considering the advantages of ZnO and AgI comprehensively, engineering ZnO/AgI heterojunction is the most promising way for increasing material stability and photocatalytic activity. For example, Huang et al. prepared carnation-like ZnO@AgI hierarchical nanostructures by depositing AgI onto ZnO for creating more photocatalytic active sites and decreasing the recombination of photoinduced electron-hole pairs [24]. Liu et al. reported a citric acid-induced hydrothermal synthesis of ZnO/AgI heterojunction for the photocatalytic degradation of rhodamine B (RhB), methyl orange (MO), and tetracycline (TC) [25].
Fabrication of a novel Ag<inf>3</inf>PO<inf>4</inf>/WO<inf>3</inf>·H<inf>2</inf>O composite with enhanced visible light photocatalytic performance for the degradation of methylene blue and oxytetracycline
2021, Inorganic Chemistry CommunicationsCitation Excerpt :Among these approaches, the construction of coupled semiconductor systems is becoming a research hotspot, because it can increase the utilization of visible light and improve the separation of the electron-hole pairs and lifetime of the carriers, thus showing a higher photocatalytic activity than single photocatalysts. In recent years, various coupled semiconductor systems have been developed for degradation of organic pollutants, including binary photocatalysts TiO2/In2O3 [18], ZnO/BiOI [19], Ag3PO4/CeO2 [20], ZnO/AgI [21], ternary photocatalysts ZnO/Ag3VO4/AgI [22], ZnO/AgBr/Ag2CO3 [23], TiO2/Bi2O3/CuO [24], Ag2CO3/CeO2/AgBr [25], etc. Recently, still more research is being carried out in coupled semiconductor systems to develop photocatalysts with high photocatalytic activity under visible light and improve the photocatalytic performances of the single photocatalysts.