Elsevier

Materials Letters

Volume 65, Issues 23–24, December 2011, Pages 3625-3628
Materials Letters

Synthesis of sea urchin-like cuprous oxide with hollow glass microspheres as cores and its preliminary application as a photocatalyst

https://doi.org/10.1016/j.matlet.2011.07.104Get rights and content

Abstract

Cuprous oxide (Cu2O) microcrystals with sea urchin-like morphologies were successfully prepared on the surface of hollow glass microspheres (HGMs) using sodium sulfite (Na2SO3) as the reducing agent and sodium acetate–acetic acid (NaAc–HAc) as buffer solution in copper sulfate (CuSO4) solution. The products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential thermal-thermogravimetry (DTA-TG), and visible spectrophotometer. Based on the SEM images of the as-obtained samples, it was found that the HGMs played a crucial role in the formation of sea urchin-like Cu2O. Meanwhile, the stirring time was also important for coating process. The as-prepared sea urchin-like microcrystals are cubic phase Cu2O. The as-prepared products can be oxidized at 240 °C. The preliminary study on the photocatalytic behavior of the sea urchin-like Cu2O showed that the photodegradation efficiency of 40 mg/L methyl orange (MO) reached 95.15% within 30 min.

Highlights

► Hollow glass microspheres as cores. ► Sea urchin-like cuprous oxide was prepared under acid conditions. ► It has a 100–200 nm diameter. ► Such product has the properties of lightweight, good dispersibility, high specific surface and photo-degradation efficiency.

Introduction

As Cu2O is a P-type semiconductor oxide with direct forbidden band gap of 2.0 eV, much attention has been paid to the fabrication of nano/micro-dimensional Cu2O in recent years owing to its unique optical and magnetic properties in solar cells [1], the negative electrode materials for lithium ion batteries [2], catalysts [3], biosensors [4], etc. As yet, Cu2O with various morphologies, such as hollow spheres [5], porous octahedron [6], bi-pyramids [7], nanoclusters [8], nanowires [9], have been synthesized by different techniques including galvanic deposition [10], thermal oxidation [11], radio frequency-magnetron sputtering [12], metalorganic chemical vapor deposition [13], and catalytic solution route [14]. In practical application, the size of Cu2O particles will be reduced as much as possible in order to obtain excellent property, which makes recycling much harder.

HGMs consist of outer stiff glass and inner inert gas, which results in some unique properties, such as low density, good dispersion, high water resistance and high thermal resistance. Based on these properties, HGMs have been used in the fabrication of coating composite materials for different applications [15], [16], [17], [18]. It can be expected that if the HGMs were coated with a layer of Cu2O, wider use would be developed in some fields, as they combine the properties of HGMs and Cu2O together.

Hence, in order to prepare Cu2O with low density, good dispersion, high specific surface, and can be recycled, a conventional chemical deposition route was utilized in this paper to coat HGMs with Cu2O in acidic solution. To obtain a uniform deposit layer, a pretreatment method was performed to improve the surface properties of the HGMs. As demonstrated, sea urchin-like Cu2O was obtained after the introduction of HGMs. In experimentation of photocatalytic activity, the sea urchin-like Cu2O can enormously reflect and diffuse visible light so as to multiply photocatalytic efficiency.

Section snippets

Raw materials

The hollow glass microspheres (Model: QH-450; diameter: 2–100 μm; apparent density: 0.1–0.11 g/cm3; wall thickness: 1–2 μm) were purchased from the Qinhuangdao Glass Sphere Company of China. All of the chemical reagents are analytical grade and were used as received without any further purification.

Pretreatment method of hollow glass spheres

Cleanliness and roughing treatment of the substrates is one of the most important factors dominating whether or not the cuprous oxide could be adsorbed on the surface of the HGMs. Hence, before the

Results and discussion

Fig. 1 shows the SEM images of the HGMs and Cu2O coated HGMs that prepared under different stirring systems, i.e. intermittent, with or without stirring. Fig. 1(a) shows that, the surface of the HGMs is rough after the pretreatment. Fig. 1(b) presents a SEM image of the Cu2O obtained under intermittent stirring, from which one can see Cu2O crystals with sea urchin-like morphology. The diameter of the Cu2O whiskers is in the range of 100–300 nm, shown as Fig. 1(e). Fig. 1(c) shows a SEM image of

Conclusions

Sea urchin-like Cu2O have been synthesized by a novel route in the presence of the HGMs, which requires no complicated apparatus, techniques, organic or polymer additives. Meanwhile, the stirring time was found to play an important role in coating process. The as-prepared Cu2O possesses distinct photocatalytic activity. The photodegradation efficiency of 40 mg/L methyl orange reached 95.15% within 30 min, which is much higher than other Cu2O samples.

Acknowledgments

This work was supported by the Shandong Provincial Natural Science Foundation (No. Y2007F43), P.R. China.

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