Elsevier

Chemical Physics Letters

Volume 730, September 2019, Pages 45-53
Chemical Physics Letters

Research paper
Research on catalytic performance and mechanism of Cu2O in dark environment and visible light

https://doi.org/10.1016/j.cplett.2019.05.036Get rights and content

Highlights

  • Cu2O was successfully synthesized at low temperature.

  • Cu2O has a good decolorization rate for MO under visible light and no light conditions.

  • The change of nuclear structure determines the stability of Cu2O.

  • The synergism between different exposed crystal surfaces can improve the performance of Cu2O.

Abstract

Cu2O micro-nanoparticles have been successfully fabricated at low-temperature. The experimental results show that the Cu2O has excellent decolorization rate for methyl orange (MO) under both non-light and visible conditions. Through analysis, It found that the catalysis of Cu2O is an electron-sensitization process. Under light condition, the nuclear structure tends to regenerate Cu2O, while under non-light condition, it tends to change to CuO. The reaction temperature will affect the morphology of Cu2O. The synergism between different exposed crystal planes makes the potential energy barrier between Cu2O and CuO increased, which improves the stability and catalytic activity.

Introduction

As a metal-oxide p-type semiconductor material, Cu2O has a narrow band gap of about 2.17 eV [1], therefore, has been considered to be a potential material for the conversion of solar energy into electrical or chemical energy. Based on this unique property, Cu2O can be used in many fields, like light-controlled conductive switching [2], [3], gas sensor [4], [5], [6], [7], visible light catalysis in solar cells [8], [9], [10], [11] and photocatalytic degradation of harmful substances [12], [13], [14], [15]. In nowadays, with the development of industry, the problem of water pollution is becoming more and more serious, but the traditional physical and chemical methods for wastewater treatment are costly, slow and not thoroughly, thus, it's urgent to seek a more cost-effective approach to eliminate environmental pollution. Due to the fact that Cu2O can utilize solar light to catalyze the organic pollutants degradation, it can be applied to the treatment of water pollution, which has drawn much attention from researchers [16], [17], [18], [19]. According to reports of the literature that the catalytic activity of Cu2O has a direct relationship with its crystal morphology [20], [21], For instance, Yang and Tang et al. [22] reported that in alkali NaCl solutions with copper as electrodes and K2Cr2O7 as additive, Cu2O spherical nanoparticles of 35 nm have been successfully synthesized via electrochemical method, and found better photocatalytic performance to MO. Yang et al. [23] synthesized sedum rubrotinctum shaped Cu2O in a water/oil (w/o) microemulsion, and found that a degradation of 98.94% was achieved in 90 min irradiation time of MB. Huang et al. [24] reported that EG was used as solvent and reducing agent to prepare cubic Cu2O nanoparticles in 181 °C oil bath, and the decolorization efficiency of MO is only 20.7% after visible-light irradiation of 7 h. Yang and Liu et al. [25] by controlling the reaction times, Cu2O samples with different morphologies of micrometer rods, hexapods, octahedral, and truncated octahedral microcrystals have been synthesized by a facile hydrothermal method, and the results show that the morphologies of the Cu2O samples influenced their catalytic activities, and the truncated octahedra with the hollow microcrystals possessed the best activity. From the previous study we can found that the preparation methods of Cu2O is varied, but all these preparation methods of Cu2O either require some high precision instruments or higher temperatures and pressures, and all of this are expensive and not easy to achieve, so choosing a way that avoided these shortcomings is becoming a viable option.

In this study, we prepared a series of Cu2O samples at low temperature by an easy to-operate, economical and time-saving liquid-phase reduction method. The morphology and composition of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and the catalytic performance to MO were evaluated using ultraviolet and visible light spectrometer (UV–vis). Different from the previous studies, in this work, the catalytic performance of Cu2O in dark has been researched emphatically.

Section snippets

Materials

Pentahydrate copper sulphate [CuSO4·5H2O, AR], sodium hydroxide (AR), glucose [C6H12O6·H2O, AR] were used in this work as received without further purification, All the aqueous solutions were prepared using deionized water.

Preparation of Cu2O

Five different Cu2O samples were synthesized at different temperatures by liquid-phase reduction method. The synthesis process diagram was shown in Fig. 1. In the typical procedure, 40 mL copper sulfate solution (1 mol/L) and 20 mL sodium hydroxide solution (5 mol/L) were

XRD patterns of the samples

The XRD patterns of all samples are shown in Fig. 2, It can be seen that all the diffraction peaks match the standard data of Cu2O (JCPDS no. 65-3288) and no additional phases were detected in the samples, which indicated that the samples prepared in this work were pure Cu2O. In addition, with the reaction temperature increasing, the intensity of Cu2O (2 0 0) peak tends to enhanced. According to reports [20], [26] that this trend may be caused by the increase of cubic Cu2O.

SEM images of the samples

The SEM images of

Conclusions

In summary, Cu2O micro-nanoparticles were prepared by the method liquid-phase reduction, and the catalytic performance of samples prepared at different reaction temperatures both under dark environments and visible light were studied. The results show that the synthesized Cu2O has good catalytic performance under both visible light and non-light conditions. In the process of electron sensitization, there are two possible changes in the nuclear structure, namely regeneration to Cu2O and

Declaration of Competing Interest

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled “Research on catalytic performance and mechanism of Cu2O in dark environment and visible Light”.

Acknowledgments

The authors are grateful for all the test provided by ‘Analytical and Testing Center of Southwest Jiaotong University’ and ‘ceshigo’ (www.ceshigo.com).

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