Article pubs.acs.org/IECR
Mesoporous Microsphere of ZnS Photocatalysts Loaded with CuO or Mn3O4 for the Visible-Light-Assisted Photocatalytic Degradation of Orange II Dye Gang-Juan Lee,† Arumugam Manivel,† Valentina Batalova,‡ Gennady Mokrousov,‡ Susan Masten,§ and Jerry Wu*,†,§ †
Department of Environmental Engineering and Science, Feng Chia University, Taichung 407, Taiwan Department of Analytical Chemistry, Tomsk State University, Tomsk, Russia § Department of Civil and Environmental Engineering, Michigan State University, East Lansing, Michigan 48824, United States ‡
ABSTRACT: Mn3O4- and CuO-modified zinc sulfide (ZnS) photocatalysts were successfully prepared and characterized by Xray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, surface area analysis, and diffuse-reflectance spectroscopy methods. The weight percentages of manganese (Mn) or copper (Cu) in the composite catalysts were maintained between 0.5% and 5%. Optical characterizations of the synthesized catalysts showed the shifted photoabsorption properties from the ultraviolet region to visible light. The band gaps of ZnS loaded with 0.5−5% Mn and Cu were calculated from the absorption edge positions and were in the ranges of 2.61−2.81 and 2.81−2.92 eV, respectively. The photocatalytic performances of the ZnS composites were evaluated for the visible-lightassisted photocatalytic decomposition of Orange II dye. ZnS loaded with 1.5 wt % Mn and 1 wt % Cu at a dosage of 0.5 g/L shows the highest photocatalytic activity, which represents 32.1% and 61.1% degradation of Orange II dye, respectively. decrease of the photoluminescence intensity.10 Because the catalytic behaviors of CuO are strongly dependent on the support properties, CuO supported on carbon-modified γAl2O3 catalysts indicates that carbon can prevent the aggregation of CuO and improve the catalytic activity.11 Hence, in the present study, ZnS photocatalysts loaded with Mn3O4 or CuO were successfully attempted and their visiblelight-driven photocatalytic activity was demonstrated for the application to degrade azo dye Orange II.
1. INTRODUCTION Much effort has been devoted in recent years to developing highly active heterogeneous photocatalysts for environmental applications, such as air purification, water disinfection, hazardous waste remediation, and wastewater treatment.1 Zinc sulfide (ZnS) has been regarded as one of the prominent photocatalysts for the photocatalytic degradation of several organic pollutants such as dyes, p-nitrophenol, and halogenated benzene derivatives in wastewater treatment.2,3 However, the wide band gap (3.66 eV) has confined its photoresponse in the ultraviolet (UV) region ( 400 nm) → CuO/ZnS (h+ vb) + CuO/ZnS (e−cb) + OII dyeads* (5) +
11910
−
OII dyeads* + CuOsurf → OII dyeads + CuOsurf (e )
(6)
CuOsurf + e−cb + CuO/ZnS (e−) → CuOsurf (e−)
(7)
CuOsurf (e−) + O2ads → CuOsurf + •O2−
(8)
h+ vb + OH−ads → •OH
(9)
dx.doi.org/10.1021/ie401815z | Ind. Eng. Chem. Res. 2013, 52, 11904−11912
Industrial & Engineering Chemistry Research
Article
Figure 10. Proposed mechanisms for the visible-light photocatalytic reaction of Orange II dye on the CuO/ZnS photocatalyst.
■
•
O2− + •OH + OII dyeads+ → degradation of the OII dye (10)
Furthermore, the effect of CuO loading on the ZnS surface as the modified photocatalyst on Orange II dye degradation is shown in Figure 10. As a result, CuO or Mn3O4 nanoparticles can scavenge the injected electron and separate photogenerated electrons and holes more effectively, which are responsible for reduction of the photogenerated hole−electron recombination rate. Thus, the Mn3O4/ZnS and CuO/ZnS composite catalysts can improve the photocatalytic activity.
4. CONCLUSIONS In summary, we have successfully synthesized Mn3O4/ZnS and CuO/ZnS composite catalysts, which have been well characterized using various spectral and analytical techniques. The obtained results demonstrate that the coupling of semiconductors Mn3O4 or CuO with ZnS gets enhanced optical properties with tuned band-gap positions, suitable for harvesting more visible light. The formed flower-like porous structures gave the added advantage of conserving the surface area for enhanced catalytic properties. XRD and XPS analyses confirmed the crystallite structure and electronic states of Mn3O4- and CuO-loaded ZnS. Their visible-light-assisted photocatalytic ability has been successfully demonstrated for degradation of an azo dye Orange II. The effect of CuO and Mn3O4 (wt %) loading on photocatalytic removal of Orange II dye, suggested that 1 wt % CuO and 1.5 wt % Mn3O4 were the optimal loadings for better photocatalytic properties.
■
REFERENCES
(1) Anandan, S.; Kathiravan, K.; Murugesan, V.; Ikuma, Y. Anionic (IO3−) Non-metal Doped TiO2 Nanoparticles for the Photocatalytic Degradation of Hazardous Pollutant in Water. Catal. Commun. 2009, 10, 1014. (2) Zhu, J.; Zach, M. Nanostructured Materials for Photocatalytic Hydrogen Production. Curr. Opin. Colloid Interfaces 2009, 14, 260. (3) Maji, S. W.; Dutta, A. K.; Srivastavs, D. N.; Paul, P.; Mondal, A.; Adhikary, B. Effective Photocatalytic Degradation of Organic Pollutant by ZnS Nanocrystals Synthesized via Thermal Decomposition of Single-source Precursor. Polyhedron 2011, 30, 2493. (4) Bao, N.; Shen, L.; Takata, T.; Domen, K. Self-templated Synthesis of Nanoporous CdS Nanostructures for Highly Efficient Photocatalytic Hydrogen Production under Visible Light. Chem. Mater. 2008, 20, 110. (5) Reddy, J. K.; Srinivas, B.; Kumari, V. D.; Subrahmanyam, M. Sm3+-Doped Bi2O3 Photocatalyst Prepared by Hydrothermal Synthesis. ChemCatChem 2009, 1, 492. (6) Maeda, K.; Nishimura, N.; Domen, K. A Precursor Route to Prepare Tantalum (V) Nitride Nanoparticles with Enhanced Photocatalytic Activity for Hydrogen Evolution under Visible Light. Appl. Catal. A 2009, 370, 88. (7) Karan, N. S.; Sarma, D. D.; Kadam, R. M.; Pradhan, N. Doping Transition Metal (Mn or Cu) Ions in Semiconductor Nanocrystals. J. Phys. Chem. Lett. 2010, 1, 2863. (8) Moses Ezhil Raj, A.; Grace Victiria, S.; Bena Jothy, V.; Ravidhas, C.; Wollschlager, J.; Suendorf, M.; Neumann, M.; Jayachandran, M.; Sanjeeviraja, C. XRD and XPS Characterization of Mixed Valence Mn3O4 Hausmannite Thin Films Prepared by Chemical Spray Pyrolysis Technique. Appl. Surf. Sci. 2010, 256, 2920. (9) Xue, X.; Ji, W.; Mao, Z.; Li, Z.; Ruan, W.; Zhao, B.; Lombardi, J. R. Effects of Mn Doping on Surface Enhanced Raman Scattering Properties of TiO2 Nanoparticles. Spectrochim. Acta, Part A 2012, 95, 213. (10) Lee, S.; Song, D.; Kim, D.; Lee, J.; Kim, S.; Park, I. Y.; Choi, Y. D. Effects of Synthesis Temperature on Particle Size/Shape and Photoluminescence Characteristics of ZnS:Cu Nanocrystals. Mater. Lett. 2004, 58, 342. (11) Wan, H.; Li, D.; Dai, Y.; Hu, Y.; Liu, B.; Dong, L. Catalytic Behaviors of CuO Supported on Mn2O3 Modified γ-Al2O3 for NO Reduction by CO. J. Mol. Catal. A: Chem. 2010, 332, 32. (12) Muruganandham, M.; Kusumoto, Y.; Okamoto, C.; Muruganandham, A.; Abdulla-Al-Mamun, Md.; Ahmmad, B. Mineralizer-assisted Shape-Controlled Synthesis, Characterization, and Photocatalytic Evaluation of CdS Microcrystals. J. Phys. Chem. C 2009, 113, 19506. (13) Muruganandham, M.; Kusumoto, Y. Synthesis of N,C-Codoped Hierarchical Porous Microsphere ZnS as a Visible Light-Responsive Photocatalyst. J. Phys. Chem. C 2009, 113, 16144. (14) Liu, Y.; Hu, J.; Ngo, C.; Prikhodko, S.; Kodambaka, S.; Li, J.; Richards, R. Gram-Scale Wet Chemical Synthesis of Wurtzite-8H
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Tel.: +886-4-24517250 Ext. 5206. Fax: +886-4-24517686. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS The authors thank the National Science Council (NSC) in Taiwan under Contract NSC-100-2632-E-35-001-MY3 for financial support. Support in providing the fabrication and measurement facilities from the Precision Instrument Support Center of Feng Chia University is also acknowledged. J.W. also acknowledges the visiting professor appointment by the Department of Civil and Environmental Engineering, Michigan State University. 11911
dx.doi.org/10.1021/ie401815z | Ind. Eng. Chem. Res. 2013, 52, 11904−11912
Industrial & Engineering Chemistry Research
Article
Nanoporous ZnS Spheres with High Photocatalytic Activity. Appl. Catal. B 2011, 106, 212. (15) Maji, S. K.; Mukherjee, N.; Mondal, A.; Adhikary, B.; Karmakar, B.; Dutta, S. Synthesis and Characterization of Nanocrystalline Zinc Sulfide via Zinc Thiobenzoate-Lutidine Single-Source Precursor. Inorg. Chim. Acta 2011, 371, 20. (16) Huang, M. H.; Mao, S.; Feick, H.; Yan, H.; Wu, Y.; Kind, H.; Webber, E.; Russo, R.; Yang, P. Room-Temperature Ultraviolet Nanowire Nanolasers. Science 2001, 292, 1897. (17) Owens, F. J.; Gladczuk, L.; Szymczak, R.; Dluzewski, P.; Wisniewski, A.; Szymczak, H.; Golnik, A.; Bernhard, Ch.; Niedermayer, Ch. High Temperature Magnetic Order in Zinc Sulfide Doped with Copper. J. Phys. Chem. Solids 2011, 72, 648. (18) Tsuji, I.; Kudo, A. H2 Evolution from Aqueous Sulfite Solutions under Visible-Light Irradiation over Pb- and Halogen-Codoped ZnS Photocatalysts. J. Photochem. Photobiol. A 2003, 156, 249. (19) Liu, Y.; Cuo, L.; Yan, W.; Liu, H. A Composite Visible-Light Photocatalyst for Hydrogen Production. J. Power Sources 2006, 159, 1300. (20) Rajabi, H. R.; Khani, O.; Shamsipur, M.; Vatanpour, V. HighPerformance Pure and Fe3+-Ion Doped ZnS Quantum Dots as Green Nanophotocatalysts for the Removal Malachite Green under UV-Light Irradiation. J. Hazard. Mater. 2013, 250−251, 370. (21) Chen, P. K.; Lee, G. J.; Anandana, S.; Wu, J. J. Synthesis of ZnO and Au Tethered ZnO Pyramid-Like Microflower for Photocatalytic Degradation of Orange II. Mater. Sci. Eng., B 2012, 177, 190. (22) Liu, Y.; Chen, X.; Li, J.; Burda, C. Photocatalytic Degradation of Azo Dyes by Nitrogen-Doped TiO2 Nanocatalysts. Chemosphere 2005, 61, 11.
11912
dx.doi.org/10.1021/ie401815z | Ind. Eng. Chem. Res. 2013, 52, 11904−11912
