Facile synthesis of CuO nanomorphs and their morphology dependent sunlight driven photocatalytic properties
Graphical abstract
Highlights
► Spherical, vesicular, platelet type and sheet-like CuO nanomorphs are synthesized. ► PVP and oxalic acid mediated chemical precipitation and hydrothermal methods are employed for synthesis. ► CuO nanomorphs mediated sunlight driven photocatalysis of methylene blue is studied. ► Platelet like CuO showed highest photoactivity towards MB degradation.
Introduction
Nanocrystalline semiconductor particles have drawn considerable interest in recent years because of their special properties such as a large surface to volume ratio, increased activity, special electronic properties and unique optical properties compared to those of the bulk materials [1], [2]. The oxides of transition metals are an important class of semiconductors. Among these transition-metal oxides, copper oxide (CuO); one of the important p-type semiconductors with a narrow band gap of 1.4 eV [3] has attracted much attention. CuO has complex magnetic phases and forms the basis for several high-Tc superconductors and materials with giant magneto resistance [4], [5]. In addition, CuO is used as optical switch, pigment, fungicide, metallurgy reagent, gas sensor, magnetic storage media, field emission (FE) emitter and solar cells owing to its photoconductive and photochemical properties [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. Recently, many studies have focused on its applications in photocatalysis. However, in most reports, CuO was used only as a sensitizer of a composite photocatalyst such as CuO/TiO2 [17], [18], [19], CuO/SnO2 [20], CuO/ZnO [21], CuO/BiVO4 [22], CuO/SiO2 [23], and CuO/zeolite [24], [25]. In these studies, the activity was not satisfactory when CuO alone was used as the photocatalyst in the control experiment. Since 2008, several groups [26], [27], [28], [29] have reported CuO of various morphologies used as the photocatalyst. The light sources were only limited to ultraviolet (UV) or ultraviolet–visible (UV–vis) light. Disadvantages of these methods are: the price of consuming scarce resources and generating pollutant emissions and waste, associated to the electricity needed. Moreover, some of the wavelengths involved are harmful and require protective measures during their use; this limits the utility of the photocatalyst. Sunlight is the key source of illumination to perform different photocatalytic reactions. Visible light is a major component of sunlight as compared to UV–vis light, which is only about 4% of total solar radiation. Due to this factor, development of a stable photocatalytic system, which should be effective in the presence of visible light, is indispensable from the view point of efficient utilization of sunlight.
Generally, the catalytic properties are affected by the morphology. This implies the importance of necessity of controlled morphological synthesis of CuO for enhanced practical applications. Similar to many functional semiconductors, many novel CuO micro/nanostructures such as networks [30], sheaf-like structures [31], nanoribbons [32], as well as caddice clew-like [33], rectangular nanobat-like [34] and peanut-like [35] structures have been fabricated by a range of techniques, including chemical vapor deposition, hydrothermal methods and some solution processes. Among the various synthesis methods utilized, hydrothermal and chemical precipitation methods are of special interest because they are safe and environmental-friendly processes performed at moderate temperatures without use of any expensive equipment.
In the present paper, we report synthesis of CuO nanostructures with different morphologies such as spherical, vesicular, nanosheet like and platelet, using chemical precipitation and hydrothermal methods. Polyvinyl pyrrolidone (PVP) and oxalic acid were used as the templates to control growth of CuO crystals. The feature of this work lies in its simplicity in controlling the growth of the various integrated nanostructures from single metal ion source using simple chemical routes. Further, the natural sunlight driven photocatalytic activities of as prepared CuO crystals were evaluated using methylene blue as a model dye contaminant. Plateletlike CuO nanostructures were found to have the best catalytic activity towards MB dye degradation.
Section snippets
Synthesis of CuO nanostructures
As summarized in Table 1, there were four major synthetic schemes used in the current work:
- (a)
3.319 g CuSO4⋅5H2O and 2 g PVP were dissolved separately in 25 ml of double distilled water. These two solutions were mixed together using magnetic stirrer at room temperature. The initial pH of the solution was 5.7. Then to this solution 10 ml of 30% hydrazine hydrate solution was added drop wise with constant stirring. The final pH of the solution was 8.5. The brown colored precipitate so formed was
Physicochemical characterization
The ability of the chemical precipitation and hydrothermal methods used to promote the formation of oxide nanostructures with low reaction temperature and ambient processing time was evaluated by characterizing the synthesized material using different characterization techniques. The crystallinity and the crystal phases of the synthesized materials were examined by X-ray diffraction (XRD) measured with Cu Kα radiation. Fig. 1 shows the XRD patterns of products obtained by four different methods.
Conclusion
CuO nanomorphs were synthesized using chemical precipitation and hydrothermal methods. Compared with the other methods such as sonochemical and sol–gel methods which require higher temperature and expensive equipments, this procedure does not require pressure controlling and higher temperature. By changing the reaction parameters such as, precipitating/reducing agent, complexing agent and the reaction temperature, CuO nanostructures of different morphologies can be grown. The properties of the
Acknowledgements
The authors would like to thank Mr. Palani Raja for experimental assistance.
References (57)
- et al.
Oxidation of organic pollutants in aqueous solutions by nanosized copper oxide catalysts
Appl. Catal. B
(2009) - et al.
Synthesis and characterization of CuO/TiO2 catalysts for low-temperature CO oxidation
Catal. Commun.
(2006) - et al.
5.1% Apparent quantum efficiency for stable hydrogen generation over eosin sensitized CuO/TiO2 photocatalyst under visible light irradiation
Catal. Commun.
(2007) - et al.
Fabrication and photocatalysis of CuO/ZnO nano-composites via a new method
Mater. Sci. Eng. B
(2008) - et al.
Fabrication and efficient photocatalytic degradation of methylene blue over CuO/BiVO4 composite under visible-light irradiation
Mater. Res. Bull.
(2009) - et al.
Solar photodecolorization of methylene blue by CuO/X zeolite as a heterogeneous catalyst
Appl. Catal. A: Gen.
(2010) - et al.
Heterogeneous photodegradation catalysis of o-phenylenediamine using CuO/X zeolite
Appl. Catal. A: Gen.
(2010) - et al.
Flower-shaped CuO nanostructures: structural, photocatalytic and XANES studies
Catal. Commun.
(2008) - et al.
CTAB-assisted synthesis and photocatalytic property of CuO hollow microspheres
J. Solid State Chem.
(2009) - et al.
From 2-D CuO nanosheets to 3-D hollow nanospheres: interface-assisted synthesis, surface photovoltage properties and photocatalytic activity
J. Solid State Chem.
(2010)
Ultralong Cu(OH)2 and CuO nanowire bundles: PEG200-directed crystal growth for enhanced photocatalytic performance
J. Colloid Interface Sci.
Synthesis of sheaf-like CuO from aqueous solution and their application in lithium-ion batteries
J. Alloy. Comp.
Self-assembled synthesis of hierarchical nanostructured CuO with various morphologies and their application as anodes for lithium ion batteries
J. Power Sources
Versatile synthesis of rectangular shaped nanobat-like CuO nanostructures by hydrothermal method; structural properties and growth mechanism
Appl. Surf. Sci.
Fine tuning of the morphology of copper oxide nanostructures and their application in ambient degradation of methylene blue
J. Colloid Interface Sci.
Preparation of Cu2O/CeO2 heterojunction photocatalyst for the degradation of acid orange 7 under visible light irradiation
Catal. Commun.
Synthesis of gold nanoparticles in Winsor II type microemulsion and their characterization
J. Colloid Interface Sci.
Photochemistry of colloidal semiconductors: onset of light absorption as a function of size of extremely small CdS particles
Chem. Phys. Lett.
Preparation of one-dimensional nickel nanowires by self-assembly process
Mater. Chem. Phys.
Structural properties and growth mechanism of flower-like ZnO structures obtained by simple solution method
Mater. Res. Bull.
Nanocrystalline copper oxide for selective solar energy absorbers
Tech. Phys. Lett.
Metal Oxide Chemistry and Synthesis
Cluster-model calculation of the electronic structure of CuO: a model material for the high Tc superconductors
Phys. Rev. B
Magnetic superstructures of cupric oxide CuO as ordered arrangements of one dimensional antiferromagnetic chains
Inorg. Chem.
Controlled synthesis and self-assembly of single-crystalline CuO nanorods and nanoribbons
Cryst. Growth Des.
Bell labs win superconductivity patent
Nature
Superconductivity copper oxides get charged up
Nature
Effects of lithium oxide on the electrical properties of CuO at low temperatures
J. Mater. Res.
Cited by (158)
Hydrothermal synthesis of Cu-substituted Ni ferrites: Structural, morphological, and magnetic properties
2024, Journal of Alloys and CompoundsRemediation of phenanthrene-contaminated soil by iron oxide/carboxylate-rich porous carbon composites from vinegar residue
2024, Journal of Environmental Chemical EngineeringPhotocatalytic degradation of methylene blue dye using biogenic copper oxide nanoparticles and its degradation pathway analysis
2024, Inorganic Chemistry CommunicationsPreferentially oriented m-tuned WO<inf>3</inf> thin-films photocatalysts for the multitargeted degradation of organic molecules
2024, Applied Surface Science AdvancesRecent developments, advances and strategies in heterogeneous photocatalysts for water splitting
2024, Nanoscale Advances