In Situ Construction of CNT/CuS Hybrids and Their Application in Photodegradation for Removing Organic Dyes.

Yanping Wang,Fuchuan Jiang,Hua Yang,Jiafu Chen,Xiaofeng Sun,Tao Xian

doi:10.3390/nano10010178

Abstract

Herein, a coprecipitation method used to synthesize CuS nanostructures is reported. By varying the reaction time and temperature, the evolution of the CuS morphology between nanoparticles and nanoflakes was investigated. It was found that CuS easily crystallizes into sphere-/ellipsoid-like nanoparticles within a short reaction time (0.5 h) or at a high reaction temperature (120 °C), whereas CuS nanoflakes are readily formed at a low reaction temperature (20 °C) for a long time (12 h). Photodegradation experiments demonstrate that CuS nanoflakes exhibit a higher photodegradation performance than CuS nanoparticles for removing rhodamine B (RhB) from aqueous solution under simulated sunlight irradiation. Carbon nanotubes (CNTs) were further used to modify the photodegradation performance of a CuS photocatalyst. To achieve this aim, CNTs and CuS were integrated to form CNT/CuS hybrid composites via an in situ coprecipitation method. In the in situ constructed CNT/CuS composites, CuS is preferably formed as nanoparticles, but cannot be crystallized into nanoflakes. Compared to bare CuS, the CNT/CuS composites manifest an obviously enhanced photodegradation of RhB; notably, the 3% CNT/CuS composite with CNT content of 3% showed the highest photodegradation performance (η = 89.4% for 120 min reaction, kapp = 0.01782 min−1). To make a comparison, CuS nanoflakes and CNTs were mechanically mixed in absolute alcohol and then dried to obtain the 3% CNT/CuS-MD composite. It was observed that the 3% CNT/CuS-MD composite exhibited a slightly higher photodegradation performance (η = 92.4%, kapp = 0.0208 min−1) than the 3% CNT/CuS composite, which may be attributed to the fact that CuS maintains the morphology of nanoflakes in the 3% CNT/CuS-MD composite. The underlying enhanced photocatalytic mechanism of the CNT/CuS composites was systematically investigated and discussed.

Highlights

Water resources, being the indispensable foundation for the survival of human beings, are getting seriously polluted due to rapid industrialization
When semiconductor photocatalysts are irradiated with sunlight, valence band (VB) holes (h+) and conduction band (CB) electrons (e−) are produced through a process of photoexcitation
We have adopted a coprecipitation approach to synthesize CuS nanostructures, and found that their morphology is highly dependent on the reaction time and temperature

Summary

Introduction

Water resources, being the indispensable foundation for the survival of human beings, are getting seriously polluted due to rapid industrialization. Wastewater largely produced from chemical industries carries a large number of harmful pollutants. As the dominant pollutants in the industrial wastewater, organic dyes, such as rhodamine B (RhB), have carcinogenic properties and seriously threaten the health of mankind and aquatic life. When semiconductor photocatalysts are irradiated with sunlight, valence band (VB) holes (h+) and conduction band (CB) electrons (e−) are produced through a process of photoexcitation. The photoproduced holes and electrons are the basic reactive species, which directly or indirectly participate in oxidation and/or reduction reactions to cause the decomposition of organic dyes into harmless inorganic molecules. The photoactivity of semiconductors are generally limited due to the ease of recombination of the photoexcited holes and electrons. Many avenues have been adopted to modify photocatalysts with the aim of facilitating the spatial separation of the photogenerated carriers and ensuring their increased utilization for photodegradation reactions [5,6,7,8,9,10]

Methods

Results

Conclusion