Hydrothermal Synthesis of TiO2-rGO By Green Chemical Method

0 downloads 0 Views 366KB Size Report
Sunlight induced degradation of organic pollutants is an ideal approach for environmental pollution control and waste water treatment. Although variety of ...
Available online at www.sciencedirect.com

ScienceDirect Materials Today: Proceedings 4 (2017) 11888–11893

www.materialstoday.com/proceedings

ICNANO 2016

Hydrothermal Synthesis of TiO2-rGO By Green Chemical Method Udayabhanua, H. Nagabhushanab, D. Sureshc, H. Rajanaikad. S.C. Sharmae, G. Nagarajua* a

Dept. of Chemistry, Siddaganga Institute of Technology, Tumkur, India Prof. CNR Rao Center for Advanced Materials, Tumkur University, Tumkur, India c Dept. of Studies and Research in Chemistry, Tumkur University, Tumkur, India d Dept. of Studies and Research in EVS, Tumkur University, Tumkur, India e Dept. of Mechanical Engineering, Dayananda Sagar University, Bangalore, India

b

Abstract Sunlight induced degradation of organic pollutants is an ideal approach for environmental pollution control and waste water treatment. Although variety of photocatalysts has been designed towards this goal, efficient degradation of organic pollutants by visible light is a challenging issue. Here we show that reduced graphene oxide (rGO) based composite with TiO2 nanoparticle (TiO2-rGO) can act as efficient visible light photocatalyst for degradation of organic pollutants. We have developed a simple and large scale synthesis method for TiO2-rGO and used them for degradation of well known carcinogenic organic dye ie., Methtylene blue under visible light. It is found that photocatalytic efficiency by TiO2-rGO under visible light is significantly higher. It is proposed that TiO2 nanoparticle offers visible light induced excitation and conductive rGO offers efficient charge separation and thus induces oxidative degradation of organic pollutant. This approach can be extended for sunlight induced degradation of different organic pollutants. Keywords: TiO2; Hydrothermal; Methylene blue; Photodegradation;

© 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY (ICNANO2016).

* Corresponding author. Tel.: +91 9620157141;. E-mail address: [email protected] 2214-7853© 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY (ICNANO-2016).

Udayabhanu et. al/ Materials Today: Proceedings 4 (2017) 11888–11893

11889

1. Introduction Photocatalytic degradation of organic dyes using semiconductor (SC) photocatalysts such as TiO2 gaining growing research interest for water purification [1-3]. However, the need of ultraviolet (UV) light for activating the photocatalysts greatly limits the technology in practical applications because of the low content of UV light in the solar spectrum (of about 2–3%). As a result, research efforts have been made at exploiting new photo-catalysts, which are photocatalytically active under visible light irradiation [4-6]. On the other hand, modified semiconductors can be sensitized by organic dyes under visible light irradiation, in which the dye rather than the SC is excited, followed by an electron transfer from the excited dye to the conduction band of the SC. Then, the electron is trapped by surface adsorbed oxygen to form various reactive oxygen species (ROSs), which are responsible for the mineralization of the dye. This process is superior to that of UV activated photocatalysis because more of sunlight can be used [7]. Graphene, a two-dimensional carbon material with unique mechanic and electronic properties, offers a good opportunity References to prepare composite materials for photocatalysis applications. Graphene is generally prepared by chemical oxidation of graphite to exfoliated sheets of graphene oxide (GO), followed by reduction with sodium borohydride or highly toxic hydrazine [8]. However, the reduced graphene oxide (rGO) dispersion tends to aggregate in aqueous solution because of the loss of surface oxygen-containing groups. 2. Experimental details 2.1.Synthesis of TiO2–rGO nanoparticles In a typical synthesis process, TiO2 (Merck) powder (2.5 g) dispersed in 10 M NaOH aqueous solution (60 mL) to this add 250 mg of Pepper extract and 100 mg of sonicated graphene oxide in 5 ml and cooked at 180 0C for 24 h in Teflon-lined autoclave (capacity 60 mL). The obtained product was subjected to washing (twice) with distilled water followed by dilute hydrochloric acid, finally washed with ethanol, and dried at 80 0C for 12 h. 3. Characterization The powder X-ray diffraction (PXRD) measurements were made using Shimadzu -7000, having a high precision vertical θ-θ goniometer at a wavelength of 1.54 Å. Morphology of the obtained product was examined by Hitachi3000 scanning electron microscope and UV visible spectrophotometer (Agilent Technologies-Cary 60). 4. Results and discussion

Fig. 1. XRD Pattern of Synthesized TiO2-rGO

11890

Udayabhanu et. al/ Materials Today: Proceedings 4 (2017) 11888–11893

Fig. 1 shows the XRD patterns of TiO2-rGO composite. No diffraction peaks of layered GO can be seen, indicating the absence of layer-stacking regularity after reduction by the Pepper extract. The XRD peaks at about at 2θ at 25.4° , 37.9° , 48.0° , 54.6 (Fig. 1) can be indexed to (101), (103, 004, and 112), (200), (105 and 211) crystal planes of anatase phase (JCPDS, no. 21-1272) showed in Fig. 1. Crystallite size of the composite were analysed using Debye–Scherer equation,

D =

0.9 λ

(1)

βCos θ

In this equation, D is crystalline size, λ is X-ray wavelength (1.54 nm), β is full-width at half maximum and θ is diffraction angle. The average crystallite size of the ZnO is in the range of 30 to 35 nm.

100

1221

% Transmittance

90

771

80

55

70 50

60 -1

477 cm

50

45 300

400

500

2000

2500

3000

600

40 0

500

1000

1500

3500

4000

4500

Wavenumber (cm-1) Fig. 2 FTIR spectra of TiO2- rGO Composite

Fig. 2 shows the FTIR spectrum of TiO2-rGO composite. FTIR spectrum shows a strong peak between 400 to 500 cm-1 belongs to the characteristic peaks of Ti-O stretching frequencies. In addition to this there is a graphene bands at 771 and 1221 cm-1 corresponds to the sp2 hybridized carbon, Hydrogen bending frequency and sp3 C-H stretching frequencies [9]. In other words there is a presence of carbon content in the synthesized TiO2-rGO composite. This clearly shows that there is a incorporation of graphene with TiO2.

Udayabhanu et. al/ Materials Today: Proceedings 4 (2017) 11888–11893

11891

Figure 3 shows the SEM images of the synthesized nanoparticles. This showing that, there is a well arranged TiO2 nanoparticles on the graphene sheets [11].

Fig. 3. SEM images of TiO2-rGO composites

4.1 Photocatalytic activity studies: Photocatalytic experiments were carried out with the help of 150 x75 mm batch reactor [12-14]. A catalytic load of 50 mg TiO2–rGO powder in 100 ml of 10 ppm of Methylene blue dye was prepared. The dye solution and catalyst was placed in the reactor and magnetically stirred with simultaneous exposure to Sun light. Then the known volume (3 ml) of slurry was drawn at specific intervals (30 min), centrifuged to remove the intervention of the catalyst and assessed using spectrophotometer (617 nm) for rate of degradation. By using the following formula, the percentage (%) of degradation of the dye can be determined. % of degradation was studied by using the equation

% of degradation =

Ci - Cf

X 100

Ci Where Ci and Cf are initial and final dye concentrations respectively.

..................

(2)

11892

Udayabhanu et. al/ Materials Today: Proceedings 4 (2017) 11888–11893

From figure 4, it is clearly shows that there is a complete degradation of 10 ppm methylene blue dye under sunlight (Visible light) irradiation with the time span of 50 minutes.

664 nm

Absorbance (a.u)

1.0

0 min 10 min 20 min 30 min 40 min 50 min

0.5

0.0 300

400

500

600

700

800

Wavelength (nm) Fig. 4. Degradation spectra of Methylene blue dye under sunlight irradiation

5. Conclusion This study demonstrates a simple green synthetic approach for the synthesis of TiO2–rGO nanoparticles using Pepper Extract as a reducing agent for the synthesis. The extract comprise of significant amounts of alkaloid capsaicinoids. These components effectively act as reducing agents and lead to the synthesis of TiO2–rGO composites. SEM image confirms the formation of Nps with an average crystallite size of 30–35 nm. Methylene blue dyes was effectively degraded under UV light illumination in the presence of TiO2–rGO. The study successfully demonstrates that facile synthesis of multifunctional TiO2-rGO nanocomposites was achieved using naturally occurring sources. Acknowledgements Authors acknowledge DST Nanomission, Govt. of India, (No. SR/NM/NS-1262/2013) for financial support. G. Nagaraju acknowledges SIT, Tumkur for constant support and encouragement for research activities.

Udayabhanu et. al/ Materials Today: Proceedings 4 (2017) 11888–11893

References [1] G. Nagaraju et.al,. Journal of Molecular Catalysis A: Chemical. 378 (2013) 213–2202. [2] G. Nagaraju et.al. Materials Letters 109 (2013) 27–303. [3] G.S. Mital et.al,. Physical Chemistry 16 (2011) 1639–1657. [4] M. Ni et.al. renewable and Sustainable Energy Reviews 11 (2007) 401–425. [5] G. Liu, T. Wu, J. Zhao, H. Hidaka and N. Serpone, Environ. Sci. Technol. 33 (1999) 2081. [6] M. R. Hoffmann, S. T. Martin, W. Choi and D. W. Bahnemann. Chem. Rev 95 (1995) 69. [7] M. A. Shannon, P. W. Bohn, M. Elimelech, J. G. Georgiadis, B. J. Marinas and A. M. Mayes, Nature. 452 (2008)301. [8] S. Shanmugasundaram and K. Horst, Angew. Chem., Int. Ed., 42 (2003) 4908. [9] S. Malato, P. Ferna ndez-Ibanez, M. I. Maldonado, J. Blanco and W. Gernjak, Catal. Today. 1 (2009) 147. [10] L. Zhao, X. Chen, X. Wang, Y. Zhang, W. Wei, Y. Sun, M. Antonietti and M. M. Titirici, Adv. Mater. 22 (2010) 3317. [11] J. He, J. Zhao, T. Shen, H. Hidaka and N. Serpone, J. Phys. Chem. B. 101(1997)9027. [12] T.Wu,G. Liu, J. Zhao,H.Hidaka andN. Serpone., J. Phys. Chem. B. 102 (1998) 5845. [13] E. Bae and W. Choi, Environ. Sci. Technol. 37 (2002) 147. [14] J. Q. Wang, J. F.Wang, Q. L. Sun,W.Wang, Z. Y. Yan,W. J. Gong and L. Min, J. Mater. Chem. 19 (2009) 6597.

11893