Journal of Nanomaterials
Volume 2017 (2017), Article ID 1978764, 5 pages
https://doi.org/10.1155/2017/1978764

Research Article

Preparation and Photocatalytic Performance of Ti₃C₂/TiO₂/CuO Ternary Nanocomposites

Yang Lu,¹ Meihuan Yao,² Aiguo Zhou,¹ Qianku Hu,¹ and Libo Wang¹

¹School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China
²School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China

Correspondence should be addressed to Libo Wang; wanglibo537@hpu.edu.cn

Received 6 January 2017; Accepted 7 March 2017; Published 3 April 2017

Academic Editor: Jim Low

Copyright © 2017 Yang Lu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Ti₃C₂/TiO₂/CuO nanocomposites were synthesized via the decomposition of a mixture of Ti₃C₂ (a novel two-dimensional carbide) and cupric nitrate under an argon atmosphere. The morphology and structures of the obtained samples were characterized. X-ray diffraction and energy dispersive spectrometer analysis indicate that the sample is composed of Ti₃C₂, anatase-TiO₂, and CuO. Scanning electron microscopy images show that CuO and TiO₂ nanoparticles were evenly distributed on the surface of Ti₃C₂. The particles size increased with an increase in the cupric nitrate content. Photocatalytic degradation of methyl orange shows that the Ti₃C₂/TiO₂/CuO nanocomposite has good photocatalytic degradation efficiency. A possible photocatalytic mechanism of the Ti₃C₂/TiO₂/CuO nanocomposites was proposed. The data indicated that CuO and Ti₃C₂ effectively promote the separation of photoelectrons from vacancies.

1. Introduction

Industrial wastewater has become one of the major factors in water pollution, and in particular, wastewater from dye industries is difficult to treat. Of the various techniques for cleaning the environment, photocatalytic degradation has been widely researched to treat pollutants that are difficult to degrade. TiO₂ and ZnO are the most widely studied photocatalysts [1, 2]. To improve the photocatalysis efficiency of TiO₂, binary nanocomposites, such as TiO₂/metal (Ag [3, 4], Au [5, 6], and Pt [7]), TiO₂/graphene [8–10], TiO₂/ZnO [11], TiO₂/CuO [12], TiO₂/(CdSe, CdS, and CdSeS) [13, 14], and TiO₂/SnO₂ [15, 16], have been extensively studied, and the results show that the binary nanocomposites perform better than the single components. Less research has been done on ternary nanocomposites [17] than on binary nanocomposites. Ti₃C₂ is a member of a family of novel two-dimensional carbides or carbonitrides called MXenes, which are synthesized by etching an A-group element from the corresponding MAX phase using hydrofluoric acid [18]. Because of its special laminated structure, Ti₃C₂ has been widely researched in many fields [19–23]. However, the resistance to oxidization of Ti₃C₂ is not good. Under hydrothermal conditions or in an oxygen atmosphere, the surface of Ti₃C₂ easily oxidizes to form TiO₂ at temperatures above 100°C [18, 24, 25]. Hence, Ti₃C₂ can be used as a precursor for TiO₂ and as a carrier for other oxides.

In this study, Ti₃C₂/TiO₂/CuO ternary nanocomposites were successfully fabricated using cupric nitrate decomposition with Ti₃C₂ under an argon atmosphere. The photocatalytic performance of Ti₃C₂/TiO₂/CuO was studied using MO as a simulated pollutant. The results show that the Ti₃C₂/TiO₂/CuO ternary composite has good catalytic activity for MO photodegradation.

2. Experimental

In these experiments, 0 g, 0.005 g, 0.01 g, 0.02 g, and 0.04 g of cupric nitrate were each dissolved in 1 mL of deionized water, and then 1 g of Ti₃C₂ powder (prepared according to the literature [18]) was added. The mixture was kept at room temperature for 24 h and then dried at 70°C in a vacuum. The Ti₃C₂/TiO₂/CuO nanocomposites were synthesized by annealing the mixture under an argon atmosphere at 500°C for 30 min. The heating rate was set at 10°C/min. The obtained samples were denoted as sample a, sample b, sample c, sample d, and sample e according to cupric nitrate masses, respectively.

The detailed procedure is represented schematically in Figure 1. In this process, the chemical reaction for the formation of Ti₃C₂/TiO₂/CuO may be expressed as follows:

Figure 1: Procedure for synthesizing the Ti₃C₂/TiO₂/CuO nanocomposite.

The crystal structure of the obtained samples was characterized using powder X-ray diffraction (XRD, Philips X’Pert-MPD system, Cu Kα radiation). The morphology and microstructures of the samples were examined using a Quanta 250 field emission gun scanning electron microscope (FEI Quanta 250 FEG-SEM) equipped with a Bruker Nano GmbH with an X-Max 30 mm² detector energy dispersive X-ray spectrometer (Bruker Quantax 200 XFlash EDS).

The photocatalytic activity of the samples was evaluated for the photodegradation of MO (20 mg/L) under UV illumination. First, the obtained powder catalyst (100 mg) was dispersed in a solution of MO (100 mL) and was magnetically stirred in the dark for 30 min to establish the adsorption equilibrium. The whole photocatalytic reaction was carried out at 10°C. The solution was then irradiated with a 175 W mercury lamp light (GGZ175, Shanghai Jiguang Special Lighting Electrical Appliance Factory, China). 5.0 mL of solution was transferred every 10 min, centrifuged to remove the catalyst, and then analyzed using a UV-vis spectrophotometer (TU-1900, Beijing Purkinje General Instrument Co. Ltd., China).

3. Results and Discussion

XRD results of the samples are shown in Figure 2. The peaks detected at 2θ = 9.02°, 18.2°, and 27.5° were assigned as the diffraction peaks of Ti₃C₂ [20]. The peaks at 25.34°, 37.90°, 48.17°, 54.02°, and 55.16° were indexed to the (101), (004), (200), (105), and (211) planes, respectively, of anatase-TiO₂ (JCPDF Number 21-1272). This means Ti₃C₂ was partially oxidized to TiO₂ after treatment at 500°C for 30 min. The oxygen came from the adsorbed water and the thermal-decomposition of cupric nitrate. Because of the low content and the small crystalline size of CuO in the nanocomposites, the XRD signal was weak and may have been covered by the robust signal of TiO₂ and Ti₃C₂. Thus, the diffraction peaks of CuO were not observed.

Figure 2: XRD patterns of the as-prepared samples.

SEM images of samples a–e are shown in Figures 3(a)–3(e). Figure 3(a) is the SEM image of the sample which was obtained by Ti₃C₂ that was kept at 500°C for 30 min under an argon atmosphere. It can be observed that the sample had a smooth surface with small nanoparticles, which may be TiO₂. Figures 3(b)–3(e) show the SEM image of the Ti₃C₂/TiO₂/CuO ternary nanocomposites. From these figures, it can be seen that a large number of CuO and TiO₂ nanoparticles were densely connected to one another on the surface of the Ti₃C₂ nanosheets. With an increase in the cupric nitrate content, the density of the particulates on Ti₃C₂ increased. The increase of the size of the nanoparticles (see Figures 3(d) and 3(e)) indicates an agglomeration of nanoparticles. It can be also observed that the thickness of the layer increased. In order to observe the distribution of different elements, sample c was further identified using EDS mapping analysis of Ti, C, O, Cu, Al, and F in SEM from the selected areas in Figure 3(f). The results show that CuO was distributed evenly on the surface of Ti₃C₂.

(a)

(b)

(c)

(d)

(e)

(f)

Figure 3: SEM images of the samples: (a) Ti₃C₂, (b–e) Ti₃C₂/TiO₂/CuO (samples a–d), and (f) EDS spectra and mapping of the marked domain in (f).

The photocatalytic activities of the samples were measured, and the results are shown in Figure 4. It can be seen that the Ti₃C₂/TiO₂/CuO nanocomposites have good photocatalytic activity. The MO quickly degraded to about 99% in 80 minutes with sample c as the catalyst. The photocatalytic activity of the nanocomposites was enhanced with an increase in the cupric nitrate content and was best when 0.01 g of cupric nitrate was added. After that, with an increase in the mass of cupric nitrate, agglomeration occurred and led to a decrease in the photocatalytic performance.

Figure 4: Curves of versus time for the photodegradation of MO with samples a–e.

A possible photocatalytic mechanism of the Ti₃C₂/TiO₂/CuO nanocomposites is shown in Figure 5. The band gap between the TiO₂ valance band (VB) and the conduction band (CB) is 3.2 eV. Under UV radiation, an electron and hole are generated on the surface of TiO₂ and CuO. Because the CB of CuO is situated below that of TiO₂, the electrons in the CB of TiO₂ are easily transferred to the CB of CuO. On the other hand, the photoelectrons of TiO₂ and CuO are transferred promptly by Ti₃C₂ because of its good electron conductivity which lowers the electron-hole recombination rate. Analysis indicates that Ti₃C₂/TiO₂/CuO exhibited a more effective electron-hole separation under UV radiation. Thus, the surface redox process by photogenerated electrons and holes occurs more easily, and, correspondingly, the photocatalytic activity of the samples significantly improved.

Figure 5: Schematic illustration of a possible photocatalytic mechanism of the Ti₃C₂/TiO₂/CuO nanocomposites.

4. Conclusion

Ti₃C₂/TiO₂/CuO ternary nanocomposites were fabricated via cupric nitrate decomposition on the surface of Ti₃C₂. Analysis indicates that the samples were composed of Ti₃C₂ nanosheets, TiO₂, and CuO nanoparticles. The photocatalytic degradation experiments showed that the Ti₃C₂/TiO₂/CuO nanocomposite has a better efficiency of electron-hole separation than TiO₂, and this significantly improved the photocatalytic activity of the nanocomposites.

Conflicts of Interest

The authors declare that there are no conflicts of interest regarding the publication of this paper.

Acknowledgments

The authors gratefully acknowledge the National Nature Science Foundation of China (51205111, 51472075), the Plan for Scientific Innovation Talent of Henan Province (134100510008), the Program for Innovative Research Team of Henan Polytechnic University (T2013-4), and Key Project of Henan Educational Committee (15A440006).

References

A. Kubacka, M. Fernández-García, and G. Colón, “Advanced nanoarchitectures for solar photocatalytic applications,” Chemical Reviews, vol. 112, no. 3, pp. 1555–1614, 2012.

M. N. Chong, B. Jin, C. W. K. Chow, and C. Saint, “Recent developments in photocatalytic water treatment technology: a review,” Water Research, vol. 44, no. 10, pp. 2997–3027, 2010.

H. Y. Chuang and D. H. Chen, “Fabrication and photocatalytic activities in visible and UV light regions of Ag@TiO₂ and NiAg@TiO₂ nanoparticles,” Nanotechnology, vol. 20, no. 10, Article ID 105704, 2009.

P. D. Cozzoli, E. Fanizza, R. Comparelli, M. L. Curri, A. Agostiano, and D. Laub, “Role of metal nanoparticles in TiO2 Ag nanocomposite-based microheterogeneous photocatalysis,” Journal of Physical Chemistry B, vol. 108, no. 28, pp. 9623–9630, 2004.

H. Li, Z. Bian, J. Zhu, Y. Huo, H. Li, and Y. Lu, “Mesoporous Au/TiO2 nanocomposites with enhanced photocatalytic activity,” Journal of the American Chemical Society, vol. 129, no. 15, pp. 4538–4539, 2007.

X.-F. Wu, H.-Y. Song, J.-M. Yoon, Y.-T. Yu, and Y.-F. Chen, “Synthesis of core-shell Au@TiO2 nanopartides with truncated wedge-shaped morphology and their photocatalytic properties,” Langmuir, vol. 25, no. 11, pp. 6438–6447, 2009.

J. Yu, L. Qi, and M. Jaroniec, “Hydrogen production by photocatalytic water splitting over Pt/TiO₂ nanosheets with exposed (001) facets,” The Journal of Physical Chemistry C, vol. 114, no. 30, pp. 13118–13125, 2010.

Y. H. Zhang, Z.-R. Tang, X. Z. Fu, and Y.-J. Xu, “TiO₂-graphene nanocomposites for gas-phase photocatalytic degradation of volatile aromatic pollutant: is TiO₂-graphene truly different from other TiO₂-carbon composite materials?” ACS Nano, vol. 4, no. 12, pp. 7303–7314, 2010.

Y. Liang, H. Wang, H. S. Casalongue, Z. Chen, and H. Dai, “TiO2 nanocrystals grown on graphene as advanced photocatalytic hybrid materials,” Nano Research, vol. 3, no. 10, pp. 701–705, 2010.

D. Zhang, Y. Wang, W. Zhang, J. Pan, and J. Cai, “Enlargement of diatom frustules pores by hydrofluoric acid etching at room temperature,” Journal of Materials Science, vol. 46, no. 17, pp. 5665–5671, 2011.

P. Bansal, N. Bhullar, and D. Sud, “Studies on photodegradation of malachite green using TiO₂/ZnO photocatalyst,” Desalination and Water Treatment, vol. 12, no. 1–3, pp. 108–113, 2009.

A. Manivel, S. Naveenraj, P. S. Sathish Kumar, and S. Anandan, “CuO-TiO₂ nanocatalyst for photodegradation of acid Red 88 in aqueous solution,” Science of Advanced Materials, vol. 2, no. 1, pp. 51–57, 2010.

J. Luo, L. Ma, T. He et al., “TiO₂/(CdS, CdSe, CdSeS) nanorod heterostructures and photoelectrochemical properties,” The Journal of Physical Chemistry C, vol. 116, no. 22, pp. 11956–11963, 2012.

J. H. Zhu, D. Yang, J. Q. Geng, D. M. Chen, and Z. Y. Jiang, “Synthesis and characterization of bamboo-like CdS/TiO₂ nanotubes composites with enhanced visible-light photocatalytic activity,” Journal of Nanoparticle Research, vol. 10, no. 5, pp. 729–736, 2008.

C. Wang, C. Shao, X. Zhang, and Y. Liu, “SnO₂ nanostructures-TiO₂ nanofibers heterostructures: controlled fabrication and high photocatalytic properties,” Inorganic Chemistry, vol. 48, no. 15, pp. 7261–7268, 2009.

Z. Liu, D. D. Sun, P. Guo, and J. O. Leckie, “An efficient bicomponent TiO2/SnO2 nanofiber photocatalyst fabricated by electrospinning with a side-by-side dual spinneret method,” Nano Letters, vol. 7, no. 4, pp. 1081–1085, 2007.

H.-I. Kim, J. Kim, W. Kim, and W. Choi, “Enhanced photocatalytic and photoelectrochemical activity in the ternary hybrid of CdS/TiO2/WO3 through the cascadal electron transfer,” Journal of Physical Chemistry C, vol. 115, no. 19, pp. 9797–9805, 2011.

Z. Y. Li, L. B. Wang, D. D. Sun et al., “Synthesis and thermal stability of two-dimensional carbide MXene Ti₃C₂,” Materials Science and Engineering: B, vol. 191, pp. 33–40, 2015.

M. Naguib, J. Come, B. Dyatkin et al., “MXene: a promising transition metal carbide anode for lithium-ion batteries,” Electrochemistry Communications, vol. 16, no. 1, pp. 61–64, 2012.

M. R. Lukatskaya, O. Mashtalir, C. E. Ren et al., “Cation intercalation and high volumetric capacitance of two-dimensional titanium carbide,” Science, vol. 341, no. 6153, pp. 1502–1505, 2013.

Q. M. Peng, J. X. Guo, Q. R. Zhang et al., “Unique lead adsorption behavior of activated hydroxyl group in two-dimensional titanium carbide,” Journal of the American Chemical Society, vol. 136, no. 11, pp. 4113–4116, 2014.

O. Mashtalir, K. M. Cook, V. N. Mochalin, M. Crowe, M. W. Barsoum, and Y. Gogotsi, “Dye adsorption and decomposition on two-dimensional titanium carbide in aqueous media,” Journal of Materials Chemistry A, vol. 2, no. 35, pp. 14334–14338, 2014.

J. Yang, B. B. Chen, H. J. Song, H. Tang, and C. S. Li, “Synthesis, characterization, and tribological properties of two-dimensional Ti₃C₂,” Crystal Research and Technology, vol. 49, no. 11, pp. 926–932, 2014.

M. Naguib, O. Mashtalir, M. R. Lukatskaya et al., “One-step synthesis of nanocrystalline transition metal oxides on thin sheets of disordered graphitic carbon by oxidation of MXenes,” Chemical Communications, vol. 50, no. 56, pp. 7420–7423, 2014.

Y. P. Gao, L. B. Wang, A. G. Zhou et al., “Hydrothermal synthesis of TiO₂/Ti3C₂ nanocomposites with enhanced photocatalytic activity,” Materials Letters, vol. 150, pp. 62–64, 2015.