A facile synthesis of Ag Modified ZnO nanocrystals with enhanced photocatalytic activity

Abstract

Ag modified ZnO (Ag/ZnO) nanocrystals were prepared by a facile and low temperature wet chemical method. The phase structures, morphologies, and optical properties of the as-prepared samples were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), the Brumauer-Emmett-Teller (BET) surface area, UV-vis diffuse reflectance spectroscopy and photoluminescence (PL) spectra, respectively. The photocatalytic performance of Ag/ZnO with diffent Ag contents was measured with the degradation of methyl orange (MO) at room temperature under UV light irradiation. The experimental results indicated that the well-crystalline ZnO nanopaticles with a size of ca. 4.5 nm exhibited a high photocatalytic activity for the degradation of MO with the apparent rate constant (k) of 1.57 ×10⁻² min⁻¹, and the photocatalytic activities of ZnO were further enhanced by modification with silver. When the Ag loading was 3mol%, Ag/ZnO showed the highest photocatalytic acitivity with a k value of 5.452×10⁻² min⁻¹, which is 3.5 and 2.5 time more than that of ZnO and commercial P25, respectively.

Keywords

ZnO / Ag / nanocrystal / photocatalyst

References

[1] Fujishima A. Electrochemical Photolysis of Water at a Semiconductor Electrode[J]. Nature, 1972, 238: 37-38.

[2] Hoffmann M., Martin S., Choi W., . Environmental Applications of Semiconductor Photocatalysis[J]. Chemical Reviews, 1995, 95(1): 69-96.

[3] Kudo A., Miseki Y. Heterogeneous Photocatalyst Materials for Water Splitting[J]. Chemical Society Reviews, 2009, 38(1): 253-278.

[4] Yu H., Irie H., Hashimoto K. Conduction Band Energy Level Control of Titanium Dioxide: Toward an Efficient Visible-Light-Sensitive Photocatalyst[J]. Journal of the American Chemical Society, 2010, 132(20): 6 898-6 899.

[5] Wang X., Li S., Yu H., . Ag₂O as a New Visible-Light Photocatalyst: Self-Stability and High Photocatalytic Activity[J]. Chemistry-a European Journal, 2011, 17(28): 7 777-7 780.

[6] Yi Z.G., Ye J.H., Kikugawa N., . An Orthophosphate Semiconductor with Photooxidation Properties under Visible-light Irradiation[J]. Nature Materials, 2010, 9(7): 559-564.

[7] Chakrabarti S., Dutta B.K. Photocatalytic Degradation of Model Textile Dyes in Wastewater Using ZnO as Semiconductor Catalyst[J]. Journal of Hazardous Materials, 2004, 112(3): 269-278.

[8] Xiong H.M., Xu Y., Ren Q.G., . Stable Aqueous ZnO@ Polymer Core — Shell Nanoparticles with Tunable Photoluminescence and Their Application in Cell Imaging[J]. Journal of the American Chemical Society, 2008, 130(24): 7 522-7 523.

[9] Gorla C., Emanetoglu N., Liang S., . Structural, Optical, and Surface Acoustic Wave Properties of Epitaxial ZnO Films Grown on (0112) Sapphire by Metalorganic Chemical Vapor Deposition[J]. Journal of Applied Physics, 1999, 85: 2 595-2 603.

[10] Kong X.Y., Wang Z.L. Polar-surface Dominated ZnO Nanobelts and the Electrostatic Energy Induced Nanohelixes, Nanosprings, and Nanospirals[J]. Applied physics letters, 2004, 84: 975-978.

[11] Carotta M., Cervi A., Di Natale V., . ZnO Gas Sensors: a Comparison between Nanoparticles and Nanotetrapods-based Thick Films[J]. Sensors and Actuators B: Chemical, 2009, 137(1): 164-169.

[12] Saito M., Fujihara S. Large Photocurrent Generation in Dye-sensitized ZnO Solar Cells[J]. Energy & Environmental Science, 2008, 1(2): 280-283.

[13] Wang Q., Geng B.Y., Wang S.Z. ZnO/Au Hybrid Nanoarchitectures: Wet-Chemical Synthesis and Structurally Enhanced Photocatalytic Performance[J]. Environmental Science & Technology, 2009, 43(23): 8 968-8 973.

[14] Zheng Y.H., Zheng L.R., Zhan Y.Y., . Ag/ZnO Heterostructure Nanocrystals: Synthesis, Characterization, and Photocatalysis[J]. Inorganic Chemistry, 2007, 46(17): 6 980-6 986.

[15] Zheng Y.H., Chen C.Q., Zhan Y.Y., . Photocatalytic Activity of Ag/ZnO Heterostructure Nanocatalyst: Correlation between Structure and Property[J]. Journal of Physical Chemistry C, 2008, 112(29): 10 773-10 777.

[16] Wang X., Wang W., Liu P., . Photocatalytic Degradation of E. coli Membrane Cell in the Presence of ZnO Nanowires[J]. Journal of Wuhan University of Technology-Materials Science Edition, 2011, 26(2): 222-225.

[17] Liu B., Zeng H.C. Room Temperature Solution Synthesis of Monodispersed Single-crystalline ZnO Nanorods and Derived Hierarchical Nanostructures[J]. Langmuir, 2004, 20(10): 4196-4204.

[18] Deng Z.W., Chen M., Gu G.X., . A Facile Method to Fabricate ZnO Hollow Spheres and Their Photocatalytic Property[J]. Journal of Physical Chemistry B, 2008, 112(1): 16-22.

[19] Lao J.Y., Wen J.G., Ren Z.F. Hierarchical ZnO Nanostructures[J]. Nano Letters, 2002, 2(11): 1 287-1 291.

[20] Chu D.W., Masuda Y., Ohji T., . Formation and Photocatalytic Application of ZnO Nanotubes Using Aqueous Solution[J]. Langmuir, 2010, 26(4): 2 811-2 815.

[21] Yu J.G., Yu X.X. Hydrothermal Synthesis and Photocatalytic Activity of Ainc Oxide Hollow Spheres[J]. Environmental Science & Technology, 2008, 42(13): 4 902-4 907.

[22] Chen C.C., Fan H.J., Jan J.L. Degradation Pathways and Efficiencies of Acid Blue 1 by Photocatalytic Reaction with ZnO Nanopowder[J]. Journal of Physical Chemistry C, 2008, 112(31): 11 962-11 972.

[23] Li D., Haneda H. Morphologies of Zinc Oxide Particles and Their Effects on Photocatalysis[J]. Chemosphere, 2003, 51(2): 129-137.

[24] Yang L.Y., Dong S.Y., Sun J.H., . Microwave-assisted Preparation, Characterization and Photocatalytic Properties of a Dumbbell-shaped ZnO Photocatalyst[J]. Journal of Hazardous Materials, 2010, 179(1): 438-443.