Elsevier

Journal of Alloys and Compounds

Volume 551, 25 February 2013, Pages 327-332
Journal of Alloys and Compounds

Solvothermal synthesis of graphene–CdS nanocomposites for highly efficient visible-light photocatalyst

https://doi.org/10.1016/j.jallcom.2012.10.037Get rights and content

Abstract

Graphene–CdS (G/CdS) nanocomposites were successfully synthesized via a facile and efficient solvothermal route. The structure and composition of the obtained nanocomposites were studied by means of X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectra (XPS), and UV–Vis spectrophotometry. XRD result showed that the CdS nanorods crystallized in a hexagonal structure. SEM and TEM observations demonstrated that a homogeneous distribution of CdS nanorods on the graphene nanosheets (GNS) was formed. FTIR and XPS analyses indicated that graphite oxide (GO) has been simultaneously reduced to GNS during the deposition of CdS nanocomposite. Furthermore, visible photocatalytic activity of the composite was tested using Rhodamine B (Rh. B) as the model contaminant. Compared with the bare GNS and CdS nanorods, the G/CdS nanocomposite displayed distinctly enhanced photocatalytic activities.

Graphical abstract

In the system, because there were many functional groups such as epoxy groups (C–O–C), hydroxyl groups (–OH), carbonyl groups (Cdouble bondO) and carboxylic acid groups (–COOH) on the surface of GO, Cd2+ could be tightly adsorbed onto the GO surface via the electrostatic interaction. In the followed process, the hydrolysis/dissociation reactions of CH4N2S in EDA solution would generate sulfur ions and cause the nucleation of CdS. The reactions proceed faster at a higher temperature and facilitate the nucleation. At the same period, the starting GO sheets were reduced to GNS due to the solvothermal treatment in EDA solution and promoted the formation of G/CdS composites ultimately during the hydrothermal period.

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Highlights

► Graphene–CdS nanocomposites were synthesized via a facile and efficient solvothermal route. ► A homogeneous distribution of CdS nanorods were coated on graphene sheets effectively. ► The graphene–CdS nanocomposites displayed distinctly enhanced photocatalytic activities.

Introduction

In recent years, the growing concerns about energy and environmental problems have stimulated extensive research on solar energy utilization [1], [2]. Artificial photosynthesis systems such as photovoltaic cells, photocatalysis, and photoelectrochemical water splitting, are highly desirable because of abundant sunlight resource and less of carbon footprint [3]. Various strategies are explored to photocatalytic degradation of organic dyes using semiconductor photocatalysts. Moreover the carbon nanostructures, acting as outstanding electron acceptors and highly conductive scaffolds, have found their applications in photocatalysis and photovoltaic conversion [4], [5], [6], [7]. Graphene, as a rising star in the carbon family, shows outstanding physical, chemical properties and excellent electrocatalytic ability because of a flat monolayer of hexagonally arrayed sp2-bonded carbon atoms tightly packed into a two-dimensional (2D) honey-comb lattice, and therefore has raised serious public concern in recent research [8], [9], [10], [11], [12]. It has also shown that the excellent properties of graphene can be extended by integrating graphene with other nanomaterials to form unique hybrid materials [13], [14], [15], [16], [17], [18], [19]. Especially, the fabrication of graphene-based semiconductor nanoparticles is expected to give graphene nanocrystal hybrids with enhanced properties, including high catalytic activity and excellent electrochemical properties. Semiconductor nanoparticles, such as ZnO, TiO2, and CdS have also been utilized extensively to decorate GNS to synthesize graphene-based nanomaterials with excellent optical and catalytic properties [20], [21], [22], [23]. Furthermore, nanoscale II–VI semiconductors exhibit the size-dependant nonlinear optical, physical and electronic properties, making them promising materials and providing possibilities of applications in several fields, such as light-emitting diodes, biologic labels, and nanoelectronics [24], [25], [26]. Among the II–VI semiconductors, CdS has shown many commercial applications including solar cells, photoelectronic devices, and photocatalysis [27], [28]. More recently, many groups have synthesized CdS nanomaterials with high photocatalytic activity for the degradation of organic pollutants under ultraviolet (UV) light irradiation [29], [30]. Meanwhile, the need of UV light greatly limits its practical applications because of the low content of UV light in the solar spectrum (of about 2–3%) [31], [32], [33]. As a result, efforts have been made at exploiting new photocatalysts that are photocatalytically active under visible light irradiation [34], [35], [36]. The visible light activated photocatalyst is superior to the UV-activated ones in that a wide spectrum of sunlight can be used. However, few papers have discussed the synthesis and properties of CdS nanorods combined with graphene composites and their application in the degradation of Rh. B under visible light irradiation.

In this work, we propose the synthesis and characterizations of G/CdS hybrid, which is composed of GNS and CdS nanorods, by a solvothermal method and study the photocatalytic activity of G/CdS by a degradation test of Rh. B under visible light. It shows that the as-prepared nanocomposite have a potential application in environmental purifications.

Section snippets

Synthesis of GO, CdS and G/CdS nanocomposites

All chemicals were of analytic grade and used without further purification. GO was prepared from natural graphite powder by using a modified Hummers method [37], [38]. G/CdS nanocomposites were synthesized via a facile solvothermal method. GO (50 mg) and Cd(CH3COO)2 (0.5 mmol) were dispersed in ethylene diamine (EDA) solution (40 mL) under vigorous stirring to form a stable suspension A. Then stoichiometric amount of CH4N2S (0.5 mmol) was added to EDA solution (20.0 mL) under vigorous stirring to

Growth and characterization of G/CdS nanocomposites

In this study, we employed a simple one-step solvothermal route to synthesize G/CdS composites. The synthesis was carried out by the solvothermal hydrolysis/dissociation of CH4N2S in the presence of GO in EDA solution of cadmium acetate dihydrate at 180 °C. In the system, because there were many functional groups such as epoxy groups (C–O–C), hydroxyl groups (–OH), carbonyl groups (Cdouble bondO) and carboxylic acid groups (–COOH) on the surface of GO, Cd2+ could be tightly adsorbed onto the GO surface via

Conclusions

In conclusion, we report an effective approach to synthesize the G/CdS composites via solvothermal method. GO has been simultaneously reduced to GNS during the deposition of CdS nanocomposite and the large 2D flexible atom-thin layer of graphene makes it easier to control the distribution of CdS on it and fabricate future photocatalytic activities. The present work opens up a new avenue to preparing G-based composite materials and provides new insights into the photocatalytic degradation of

Acknowledgements

This work was supported by National Natural Science Foundation of China (Grant Nos. 51172102 and 50801065) and “Top Hundred Talents Program’’ of Chinese Academy of Sciences for financial support.

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