Preparation of ZnO flower/reduced graphene oxide composite with enhanced photocatalytic performance under sunlight

doi:10.1016/j.ceramint.2014.11.086

Ceramics International

Volume 41, Issue 3, Part A, April 2015, Pages 4007-4013

https://doi.org/10.1016/j.ceramint.2014.11.086 Get rights and content

Abstract

Reduced graphene oxide (RGO) coated ZnO flower was synthesized by a simple one-pot hydrothermal method. The morphology and properties of ZnO/RGO composites were characterized by UV–vis spectroscopy, Raman spectroscopy, SEM, TEM, EDX, XRD, photoluminescence spectroscopy and photocurrent measurement. It was found that the ZnO flowers were effectively covered with RGO sheets and formed a network structure. The photocatalytic activities of the as-prepared composites were investigated by photodegrading methylene blue under both UV light and sunlight. Results show that the ZnO/RGO composites exhibited a remarkably enhanced photocatalytic efficiency compared to pure ZnO flowers. The cause of the enhanced photocatalytic performance could be ascribed to the synergistic effect between ZnO flowers and RGO sheets. Moreover, we found that the content of graphene oxide introduced into composite material was a crucial factor for its improved photocatalytic performance.

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)

L. Li et al.
Recent progress of one-dimensional ZnO nanostructured solar cells
Nano Energy
(2012)
J. Gomez et al.
Zinc oxide nanostructuresfrom growth to application
J. Mater. Sci.
(2013)
H. Li et al.
Ultrasound-assisted preparation, characterization and properties of flower-like ZnO microstructures
Scr. Mater.
(2009)
L. Xu et al.
ZnO with different morphologies synthesized by solvothermal methods for enhanced photocatalytic activity
Chem. Mater.
(2009)
S. Suwanboon et al.
Optical and photocatalytic properties of La-doped ZnO nanoparticles prepared via precipitation and mechanical milling method
Ceram. Int.
(2013)
A. Yu et al.
Micro-lotus constructed by Fe-doped ZnO hierarchically porous nanosheetspreparation, characterization and gas sensing property
Sensors and Actuators B: Chem.
(2011)
C. Zhang
The influence of post-growth annealing on optical and electrical properties of p-type ZnO films
Mater. Sci. Semicond. Process.
(2007)
M. Seo et al.
Piezoelectric and field emitted properties of controlled ZnO nanorods on cnt yarns
Mater. Lett.
(2013)
R. Li et al.
Synthesis and UV-shielding properties of ZnO- and CaO-doped CeO₂ via soft solution chemical process
Solid State Ion.
(2002)
N. Talebian et al.
Controllable synthesis of ZnO nanoparticles and their morphology-dependent antibacterial and optical properties
J. Photochem. Photobiol. B: Biol.
(2013)

Y. Gong et al.

A facile approach to synthesize rose-like ZnO/reduced graphene oxide compositefluorescence and photocatalytic properties

J. Mater. Sci.

(2014)

Y. Zhu et al.

Hierarchical rhombus-shaped ZnO arraysynthesis, formation mechanism and solar cell application

J. Alloys Compd.

(2014)

B.S. Ong et al.

Stable, solution-processed, high-mobility ZnO thin-film transistors

J. Am. Chem. Soc.

(2007)

J. Zhao et al.

Photocatalytic oxidation for indoor air purificationa literature review

Build. Environ.

(2003)

Z. Chen et al.

Synthesis of graphene-ZnO nanorod nanocomposites with improved photoactivity and anti-photocorrosion

CrystEngComm

(2013)

T.N. Lambert et al.

Synthesis and characterization of titania-graphene nanocomposites

J. Phys. Chem. C

(2009)

B. Li et al.

Zno@graphene composite with enhanced performance for the removal of dye from water

J. Mater. Chem.

(2011)

S. Gayathri et al.

Synthesis of ZnO decorated graphene nanocomposite for enhanced photocatalytic properties

J. Appl. Phys.

(2014)

H.R. Pant et al.

A green and facile one-pot synthesis of AgNo/RGO nanocomposite with effective photocatalytic activity for removal of organic pollutants

Ceram. Int.

(2013)

H.R. Pant et al.

Zno micro-flowers assembled on reduced graphene sheets with high photocatalytic activity for removal of pollutants

Powder Technol.

(2013)

L. Zhang et al.

Green synthesis of flower-like ZnO decorated reduced graphene oxide composites

Ceram. Int.

(2014)

Cited by (119)

Effect of graphene oxide coatings on the optical properties of pulsed laser deposited ZnO:Zn thin films
2023, Optical Materials
Highly c-axis orientated ZnO:Zn thin films were successfully prepared by pulsed laser deposition and coated with graphene oxide (GO) using nebulizer spray coating. The structural, morphological, and optical properties of the films were studied before and after annealing under different conditions to produce reduced GO (rGO). Following deposition on the surface of the ZnO:Zn films, the GO sheets showed non-uniform and defective textures. Heavily crumbled sheets were observed for rGO annealed in Ar, while wrinkled sheets were observed for rGO annealed in Ar/H₂. The uncoated ZnO:Zn exhibited ultraviolet emission at ∼390 nm attributed to the recombination of excitons and a broad band in the range 400–600 nm centred at ∼450 nm attributed to zinc interstitials. The blue emission at ∼450 nm of ZnO:Zn was enhanced after coating with GO and/or rGO, which was attributed to the coupling of the light-emitting centres with localized surface plasmon resonances from the GO/rGO sheets. However, it was found that annealing of uncoated films also improved their luminescence intensity. These results showed that rGO/ZnO films may be useful for some optoelectronic or photoluminescence applications requiring ultraviolet and blue/green light.
The interface design and properties enhancement of ZnO/cellulose composites: Branching fiber network to guide the assembly of ZnO flower
2023, Journal of Colloid and Interface Science
Using renewable biomass resources to regulate the growth and properties of catalysts is sustainable nanotechnology for achieving efficient photocatalysis and recycling. This work suggested a way to produce paper-based photocatalysts and resize the embedded zinc oxide (ZnO) flowers. The combination of experimental analysis and theoretical simulations demonstrated that small pores of the branching fiber network enhanced the interfacial interaction between ZnO flowers and cellulose fibers, thereby improving mechanical properties and optimizing flower structure. The interaction energy and electron density difference (EDD) simulation results demonstrated that the ZnO/cellulose interface structure shares significant attraction and charge transfer. Cellulose fibers ground for 20 cycles (CFG20) possessed dense branching fiber network and loaded with the smallest ZnO flowers, achieving a balance of strong mechanical properties and reaction efficiency. Remarkably, ZnO/CFG20 paper-based catalyst indicated strong photodegradation efficiency (100% for methyl orange, 100% for phenol, and 85.23% for aniline) and excellent reusability. This work will pave the way for the green regulation of catalysts.
Hierarchical ZnO/MXene (Nb<inf>2</inf>C and V<inf>2</inf>C) heterostructure with efficient electron transfer for enhanced photocatalytic activity
2022, Applied Surface Science
Recently, MXene has attracted much attention as photocatalysts for efficient pollutant degradation in the field of environmental remediation but a rapid recombination of photogenerated carriers usually leads to a decrease in the photocatalytic performance. Constructing a heterostructure is considered as an effective way to improve the catalytic performance of MXene-based photocatalysts due to the promoted interfacial electron transfer. In this work, the chimeric ZnO nanosheets with good carrier mobility were formed on the accordion-shaped MXene (Nb₂C and V₂C) surface to construct hierarchical ZnO/MXene heterostructure as a photocatalyst for dye degradation. The obtained ZnO/Nb₂C and ZnO/V₂C hierarchical structure exhibited excellent photocatalytic performance in the degradation of methylene blue (MB): the degradation rate reached 62.62% and 99.53%, respectively, after irradiation with ultraviolet light for 120 min. Also, the apparent degradation rate constants (k) were 0.00777 min⁻¹ and 0.04317 min⁻¹, respectively, which were 2.92 and 16.23 times higher than those of pure ZnO. This was probably attributed to the heterostructures between ZnO and MXene which could shorten the carrier transfer path, which could facilitate the transfer of photo-generated electrons from conduction band (CB) of ZnO to CB of MXene, thereby significantly improving the photocatalytic degradation efficiency. In addition, the ZnO/Nb₂C and ZnO/V₂C hierarchical structure showed good photocatalytic stability: the degradation rate remained at 58.6% and 97.3%, respectively, after 4 cycles while it only maintained at 22.0% for pure ZnO because the obtained ZnO/MXene hierarchical structure could provide uniform active sites on the surface and porous structure, preventing the aggregation of ZnO or MXene. Therefore, this work could provide a feasible design strategy to improve the catalytic performance of 2D photocatalysts and shed a light on the design of other photocatalysts.
Synthesis and characterization of ZnO-GO composites with their piezoelectric catalytic and antibacterial properties
2022, Journal of Environmental Chemical Engineering
A simple ZnO-GO nanocomposite was prepared by hydrothermal method at room temperature, which could degrade MB, RhB and MO organic dye pollutants in the darkness with ultrasound-driven piezoelectric catalysis effect. The MB was completely degraded after 20 min with ultrasound vibration process. The various amount of nanocomposite was used to investigated the degradation effect. In addition, it was confirmed that the piezoelectric efficiency of ZnO-GO composite was better than pure ZnO. The oxidizing hydroxyl radical (•OH) and superoxide radicals (•O₂^-) are confirmed by the radical scavenger experiment in the piezocatalytic progress. The nanocomposites have excellent antibacterial activity against E. coli illustrated by the inhibition zones variation. The superoxide radical and hydroxyl radical increased by the rapid charge transfer between ZnO and GO in the synthesized system. The mechanism of the electronic transfer by the piezoelectric catalyzed process was also discussed.
Green chemistry approach for the functionalization of reduced graphene and ZnO as efficient supercapacitor application
2021, Journal of Molecular Structure
Citation Excerpt :
The D-band is a measure of defects and disorders present in the materials whereas the G-band originates due to E2g symmetric stretching of sp2 hybridized C=C bond. The Raman spectra of ZnO–GO composites have both the D and G peaks along with the characteristic vibrational mode of ZnO at 400 cm−1 [21–23]. The FT-IR spectra of GO, RGO and ZnO/RGO nanocomposite are appeared in Fig. 8.
Graphene is an allotrope of carbon consisting of a single layer atoms in a two dimensional honeycomb lattice. It has excellent electrochemical stability and possible change in physical and chemical properties. Electrodes are the primary determinants of supercapacitor electrochemical efficiency, so designing and fabricating electrodes with acceptable structural and chemical properties is critical for developing high-performance energy storage devices. The force makes graphene easy to agglomerate the reduce of the specific surface area and ratio of capacity. In this study, the graphene oxide reduced by plant leaf and then ZnO/RGO composites were synthesized by hydrothermal preparation of precursors and then calcination of precursors into composites. The phase structure and micromorphology were characterized by XRD, SEM, Raman and FT-IR. It was found that ZnO nanoparticles were embedded in the graphene sheets and form a composite structure. The electrochemical properties of the material were tested. The results show that the incorporation of graphene and Zinc oxide acted as an electrode material. The results concluded that the ZnO/RGO composite has excellent cycle stability, after 2000 cycles the average specific capacitance retention remains 80%. This is benefit from the introduction of graphene sheets and ZnO uniformly load between the sheets of graphene. The nano structure of reduced graphene oxide provides a conductive nature and more active sites for electrochemical reaction. The results prove that the incorporation of graphene and Zinc oxide are effectively reversible nature and good electrode material.
Enhanced thermal diffusivity of water based ZnO nanoflower/rGO nanofluid using the dual-beam thermal lens technique
2021, Nano-Structures and Nano-Objects
In this paper we report the results of the thermal diffusivity of water based ZnO nanoflower and ZnO nanoflower/rGO composites prepared by varying the rGO concentrations (3.3%, 4.8% and 6.3%, labelled as ZnO/rGO1, ZnO/rGO2 and ZnO/rGO3, respectively) using an in situ hydrothermal method. The dual beam thermal lens technique has been employed for the study of the thermal diffusivity of the samples. It is observed that the ZnO Nano fluid shows better thermal diffusivity compared to water and on further investigations with the ZnO/rGO composites we observed that the ZnO/rGO1 nanofluid displays an enhanced thermal diffusivity by 2.5 times that of the ZnO nanofluid. The experiments also give a great insight into the optimum value of the ZnO/rGO compositions for efficient thermal diffusion, inter-particle interaction, as well as its dependence on Brownian motion and agglomeration dynamics in nanofluid experiments.

View all citing articles on Scopus

View full text

Preparation of ZnO flower/reduced graphene oxide composite with enhanced photocatalytic performance under sunlight

Abstract

Introduction

Section snippets

Materials

Preparation of ZnO flower/reduced graphene oxide composite

Characterization of photocatalysts

Conclusion

Acknowledgments

Recent progress of one-dimensional ZnO nanostructured solar cells

Nano Energy

Zinc oxide nanostructuresfrom growth to application

J. Mater. Sci.

Ultrasound-assisted preparation, characterization and properties of flower-like ZnO microstructures

Scr. Mater.

ZnO with different morphologies synthesized by solvothermal methods for enhanced photocatalytic activity

Chem. Mater.

Optical and photocatalytic properties of La-doped ZnO nanoparticles prepared via precipitation and mechanical milling method

Ceram. Int.

Micro-lotus constructed by Fe-doped ZnO hierarchically porous nanosheetspreparation, characterization and gas sensing property

Sensors and Actuators B: Chem.

The influence of post-growth annealing on optical and electrical properties of p-type ZnO films

Mater. Sci. Semicond. Process.

Piezoelectric and field emitted properties of controlled ZnO nanorods on cnt yarns

Mater. Lett.

Synthesis and UV-shielding properties of ZnO- and CaO-doped CeO2 via soft solution chemical process

Solid State Ion.

Controllable synthesis of ZnO nanoparticles and their morphology-dependent antibacterial and optical properties

J. Photochem. Photobiol. B: Biol.

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.

Synthesis and UV-shielding properties of ZnO- and CaO-doped CeO₂ via soft solution chemical process