Electrospinning of CeO2–ZnO composite nanofibers and their photocatalytic property
Introduction
With the industrialization and civilization, environmental problems such as organic pollutants and toxic water pollutants are becoming more and more serious. ZnO, as a well-known wide direct band gap (Eg = 3.37ev at 300 K) semiconductor, has attracted much attention in recent years [1], [2] for its potential application in environment improvements. Various kinds of ZnO nanostructures, such as nanoparticle, hollow sphere have been prepared for many applications [3], [4], [5]. Especially, due to the large aspect ratios of fibers, ZnO nanofiber and its based composite nanofibers, including ZnO–SnO2, TiO2–ZnO and Ag–ZnO composite nanofibers, have revealed superior photocatalytic activity than other types, and have been mainly used as photocatalyst to degrade dye pollutants [6], [7], [8].
Ceria (CeO2), as a fascinating rare earth material, has attracted much attention due to its applications in catalysis and chemical materials [9], [10]. Accordingly, it was interesting to prepare CeO2–ZnO composites, and various efforts have been extensively developed. He et al. reported the CeO2–ZnO microspheres prepared by combining homogeneous precipitation with micro-emulsion, revealing high catalytic activity for the oxidative coupling of methane [11]. Mishra et al. prepared nanoparticle catalysts of CeO2–ZnO composites by amorphous citrate method, and they found that the presence of ceria in the composite oxide could enhance the catalytic activity for both cyclohexanol dehydrogenation and hydrogen transfer reactions [12]. However, due to the problems of aggregation and difficulties in recovery, these nanostructures might decrease the catalytic efficiency or even re-pollute the treated water or air. As is well known, electrospun composite fibers usually with porous structures possess a higher surface area that is propitious to their applications [13]. Therefore, it was significant to prepare long and ultra-fine CeO2–ZnO fibers, which might overcome the drawbacks of the nanoparticles. Unfortunately, to our best knowledge, little attention has been given to the synthesis of CeO2–ZnO nanofibers and characterization on their properties so far. In this paper, we reported a simple and inexpensive method to fabricate composite nanofibers of CeO2–ZnO, and the photocatalytic activity of the nanofibers towards the decomposition of RhB.
Section snippets
Experimental
In a typical experiment, 1.3 g of PVP was dissolved in 12 mL of 2:1(v/v) ethanol/water co-solvent. Then, 0.22 g of zinc acetate, 0.434 g of Ce(NO3)3·6H2O and three or four drops of acetic acid were added into the PVP solution. After being stirred at room temperature for 6 h, the precursor solution of PVP/Ce(NO3)3/Zn(CH3COO)2 composites was transferred to a syringe for electrospinning.
The self-made electrospinning apparatus, consisting of a high voltage supply (Glassman high voltage, FC60P2), a
Results and discussion
The SEM micrographs and the corresponding diameter distribution charts of PVP/Ce(NO3)3/Zn(CH3COO)2 composites and the fibers calcined at 600 °C are shown in Fig. 1. It could be seen that the as-spun nanofibers (Fig. 1a), with the average diameter of ~ 227 nm, have smooth and uniform surfaces. After the calcination treatment, the composite nanofibers (Fig. 1b) still remained the non-woven nanofiber morphology. However, due to the decomposition of the PVP and metal-salt, the nanofibers exhibited
Conclusions
In summary, by using sol–gel process and electrospinning technology, the CeO2–ZnO nanofibers with average diameter of 46 nm were successfully fabricated. The produced fibers were characterized by SEM, FTIR, XRD and TEM. The results showed that such composite nanofibers were composited of cubic fluorite CeO2 and hexagonal wurtzite ZnO. The morphology was also kept as continuous lines with uniform size after the annealing treatment. The investigation of photocatalytic ability indicated that the CeO
Acknowledgements
This work was supported by NSF of China (Nos. 10874153, 50772100, 50972130, and 20701033), Zhejiang provincial NSF (No. Y407188) and Science Foundation of Zhejiang Sci-Tech University.
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