Preparation of ZnO flower/reduced graphene oxide composite with enhanced photocatalytic performance under sunlight
Introduction
Zinc oxide (ZnO) is an important wide band gap (3.37 eV) semiconductor material that has become a subject of intensive scientific scrutiny [1], [2], [3], [4]. Due to the fact that ZnO owning a wide range of unique properties, it has been effectively applied in various fields, including light-emitting diodes, nanolasers, piezoelectric devices, UV-shielding materials, antibacterial agent, field-effect transistors, solar cells and gas sensors [5], [6], [7], [8], [9], [10]. As it is such a multifunctional material, designing specific structured ZnO is important for enhancing its certain properties. For example, Gong and co-workers prepared a rose-like ZnO in a mixed binary solvent that consisted of DMF and water [11]. They found the rose-like ZnO exhibited an enhancement in fluorescence properties. Zhu and co-workers synthesized a rhombus-shaped ZnO array by an one-pot synthesis method [12]. The prepared rhombus-shaped ZnO array was employed for dye-sensitized solar cell and showed a significant enhancement in short-circuit current density. Besides the above-mentioned applications, ZnO is also regarded as an excellent photocatalytic material towards degradation of many dyes and metal ions in the water purification system [5], [13]. Although nano-sized ZnO usually performs a higher photocatalytic activity due to the high surface area, the agglomeration and difficulty to recover from the reaction system are two major problems restrict its practical application [14]. Therefore, designing a micro-sized ZnO with a high surface area is an alternative pathway to overcome these problems.
In order to further enhance the photocatalytic activity of ZnO, linking ZnO with other materials such as noble metals, semiconductors and carbon based materials, has shown an improvement of photocatalytic activity by reducing the electron–hole pair recombination rate [15]. Among them, graphene has been attracted lots of attentions by many scientific researchers due to its exceptional electron-transport property [16], [17]. Recently, Gayathri and co-works prepared a ZnO decorated graphene nanocomposite by a chemical precipitation method and showed the enhanced photocatalytic performance [18]. Thus, attempts to combine the micro-sized ZnO with graphene is expected to show good photocatalytic activity and easiness for recovery from the reaction system. Herein, we reported a simple one-pot method for synthesizing ZnO flower/reduced graphene oxide (ZnO/RGO) composite using zinc nitrate hexahydrate and graphene oxide (GO) as precursors. The enhanced photocatalytic activity of ZnO/RGO composite has been observed under UV light and sunlight irradiation.
Section snippets
Materials
Zinc nitrate hexahydrate (Zn(NO3)2•6H2O) and hydrazine solution (25% in water) were purchased from Sigma-Aldrich. Graphene oxide powder was purchased from JCNANO, INC. All other chemicals used were AR grade and used without any further purification.
Preparation of ZnO flower/reduced graphene oxide composite
In this work, ZnO flower/reduced graphene oxide samples were prepared by the following procedure. GO dispersion (0.5 mg/mL) was prepared by 1 h sonication. Then, the required amount of zinc nitrate solution (50 mM) was gradually added into the GO
Characterization of photocatalysts
FE-SEM images of ZnO flower, ZnO/RGO-1, ZnO/RGO-2 and ZnO/RGO-3 composite are shown in Fig. 1. It can be found that the pristine ZnO (Fig. 1a) formed a micro-sized flower structure under the hydrothermal condition, which contains numerous ZnO rods uniting at one junction with an average length of 1 μm. The size of ZnO flowers decreases when the GO dispersion was added during the preparation process (Fig. 1b–d). It could be explained that well dispersed GO sheets provide numerous negatively
Conclusion
In summary, ZnO flower/RGO composite was synthesized via a simple one-step hydrothermal method using hydrazine as the reduce agent. The UV–vis and Raman spectroscopy results confirmed that the graphene oxide in the result composite is reduced form. The interactions of ZnO flower with RGO sheets were investigated by XRD, EDX, PL and photocurrent measurements. The ZnO/RGO composites displayed enhanced photocatalytic activity toward degradation of MB under both UV and natural sunlight irradiation
Acknowledgments
L.F. acknowledges the Swinburne University Postgraduate Research Award (SUPRA) for supporting this work.
References (42)
- et al.
Recent progress of one-dimensional ZnO nanostructured solar cells
Nano Energy
(2012) - et al.
Zinc oxide nanostructuresfrom growth to application
J. Mater. Sci.
(2013) - et al.
Ultrasound-assisted preparation, characterization and properties of flower-like ZnO microstructures
Scr. Mater.
(2009) - et al.
ZnO with different morphologies synthesized by solvothermal methods for enhanced photocatalytic activity
Chem. Mater.
(2009) - et al.
Optical and photocatalytic properties of La-doped ZnO nanoparticles prepared via precipitation and mechanical milling method
Ceram. Int.
(2013) - et al.
Micro-lotus constructed by Fe-doped ZnO hierarchically porous nanosheetspreparation, characterization and gas sensing property
Sensors and Actuators B: Chem.
(2011) The influence of post-growth annealing on optical and electrical properties of p-type ZnO films
Mater. Sci. Semicond. Process.
(2007)- et al.
Piezoelectric and field emitted properties of controlled ZnO nanorods on cnt yarns
Mater. Lett.
(2013) - et al.
Synthesis and UV-shielding properties of ZnO- and CaO-doped CeO2 via soft solution chemical process
Solid State Ion.
(2002) - et al.
Controllable synthesis of ZnO nanoparticles and their morphology-dependent antibacterial and optical properties
J. Photochem. Photobiol. B: Biol.
(2013)
A facile approach to synthesize rose-like ZnO/reduced graphene oxide compositefluorescence and photocatalytic properties
J. Mater. Sci.
Hierarchical rhombus-shaped ZnO arraysynthesis, formation mechanism and solar cell application
J. Alloys Compd.
Stable, solution-processed, high-mobility ZnO thin-film transistors
J. Am. Chem. Soc.
Photocatalytic oxidation for indoor air purificationa literature review
Build. Environ.
Synthesis of graphene-ZnO nanorod nanocomposites with improved photoactivity and anti-photocorrosion
CrystEngComm
Synthesis and characterization of titania-graphene nanocomposites
J. Phys. Chem. C
Zno@graphene composite with enhanced performance for the removal of dye from water
J. Mater. Chem.
Synthesis of ZnO decorated graphene nanocomposite for enhanced photocatalytic properties
J. Appl. Phys.
A green and facile one-pot synthesis of AgNo/RGO nanocomposite with effective photocatalytic activity for removal of organic pollutants
Ceram. Int.
Zno micro-flowers assembled on reduced graphene sheets with high photocatalytic activity for removal of pollutants
Powder Technol.
Green synthesis of flower-like ZnO decorated reduced graphene oxide composites
Ceram. Int.
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