Visible light-driven CdSe nanotube array photocatalyst
© Zhu and Li; licensee Springer. 2013
Received: 21 January 2013
Accepted: 26 March 2013
Published: 16 May 2013
Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage
KeywordsNanotube arrays Template synthesis II-VI semiconductors Visible light photocatalysis
The development of nanometer-sized photocatalysts for efficient degradation of organic pollutants has attracted continuous research attention [1–4]. Among various morphologies of nanostructures, well-aligned pseudo-one-dimensional (1D) nanostructures such as nanowire (NW) or nanotube (NT) arrays are of particular interest, since the specific morphology brings in several advantages: Its large surface-to-volume ratio prompts the surface-related chemical reactions, which is critical in most of the catalytic processes; when organized into arrays, the ordered NW/NT provides a direct pathway for charge carrier transfer to the conductive substrate. In addition, the NW/NT arrays may enhance light absorption by reducing the reflection or extending the optical path in the nanostructures [5, 6].
The most extensively studied NW/NT array photocatalyst for photodegradation of organic pollutants is the titanium dioxide (TiO2) nanotube arrays, as it is environmentally benign, capable of total mineralization of organic contaminants, easy to fabricate, and cheap. Nevertheless, its large bandgap (3.2 eV for anatase and 3.0 eV for rutile) only allows the absorption in UV range of the solar spectrum. Although doping TiO2 with elements, such as V, Cr, Mn, Fe, C, N, S, F, etc., could extend the absorption spectrum of TiO2 to the visible region, other problems occur and lead to the decrease in the quantum efficiency [7, 8]. Alternatively, direct employment of the narrower bandgap materials as the photocatalyst has been proposed as a possible solution. A few semiconductors have been investigated, such as II-VI materials (e.g., CdS [2, 9] and CdSe [10, 11]) and transition metal oxides (e.g., WO3[12–14], Fe2O3[15–18], Cu2O , Bi2WO6[20, 21], and ZnFe2O4). Nevertheless, most of the photocatalysts developed are the nanoparticles, which would not enjoy the advantage of the 1D morphology. In addition, after the nanoparticles are dispersed in the waste water for the catalytic reactions, it is troublesome to collect them after use.
In the present work, well-aligned CdSe nanotube arrays on indium tin oxide (ITO)/glass are obtained by electrodepositing CdSe on the surface of ZnO nanorod followed by ZnO etching. Such nanotube arrays exhibit strong light absorption and high photocurrent in response to the visible light. Moreover, the nanotube arrays exhibit good visible light-driven photocatalytic performance, as revealed by the photodegradation of methylene blue (MB) in aqueous solution. The charge carrier flow during the degradation process and mechanism of MB degradation are also discussed.
The CdSe nanotube arrays were synthesized via a ZnO nanorod template method, the detail of which can be found elsewhere [23–25]. Briefly, ZnO nanorod arrays were first fabricated on ITO/glass (10 Ω/□) using the hydrothermal method [26–29]. Next, CdSe nanoshells were electrodeposited on the surface of ZnO nanorods from an aqueous solution galvanostatically (at approximately 1 mA/cm2) at room temperature in a two-electrode electrochemical cell, with the nanorod array on ITO as the cathode and Pt foil as the anode. The deposition electrolyte contains 0.05 M Cd(CH3COO)2, 0.1 M Na3NTA (nitrilotriacetic acid trisodium salt), and 0.05 M Na2SeSO3 with excess sulfite [30, 31]. After approximately 7 min of electrodeposition, the ZnO/CdSe nanocable arrays were dipped into a 25% ammonia solution at room temperature for 30 min to remove the ZnO core - a process that leads to the formation of nanotube arrays on ITO. Finally, the nanotube samples were annealed at 350°C under Ar atmosphere for 1 h.
The general morphology and the crystallinity of the samples were examined by scanning electron microscopy (SEM; Quantum F400, FEI Company, Hillsboro, USA) and X-ray diffraction (XRD; Rigaku SMARTLAB XRD, Tokyo, Japan), respectively. Their detailed microstructure and chemical composition were investigated using transmission electron microscopy (TEM; Tecnai 20 FEG, FEI Company) with an energy-dispersive X-ray (EDX) spectrometer attached to the same microscope. Optical absorption was measured using a Hitachi U3501 spectrophotometer (Hitachi, Tokyo, Japan). Photoelectrochemical measurements were carried out in a three-electrode electrochemical cell using an electrochemical workstation (CHI660C, Shanghai Chenhua Instruments Co., Ltd., Shanghai, China) with 0.35 M Na2SO3 and 0.24 M Na2S solution as the hole scavenger electrolyte, CdSe nanotube arrays on ITO as the working electrode, Ag/AgCl as the reference electrode, and Pt foil as the counter electrode. The illumination source was the visible light irradiation (100 mW/cm2) from a 150-W xenon lamp (Bentham IL7, Berkshire, UK) equipped with a 400-nm longpass filter. Photocatalytic activities of the nanotube arrays were evaluated from the degradation of 0.5 ppm MB aqueous solution (5 ml) with and without adding 10 vol.% ethanol. The degradation process was monitored by measuring the absorbance of the MB solution at 664 nm using Hitachi U3501 spectrophotometer every 0.5 h.
Results and discussion
Morphology, crystal structure, and chemical composition
Further evidence for the proposed photodegradation mechanism is obtained by adding ethanol (10 vol.%) to the MB aqueous solution. This alcohol has been found to scavenge both holes and · OH radicals . As a result, MB degradation is completely quenched after adding ethanol (green symbols in Figure 4), supporting that the photogenerated holes and/or · OH radicals are mainly responsible for the MB degradation.
In conclusion, large-scale CdSe nanotube arrays on ITO have been obtained by electrodepositing CdSe on the surface of ZnO nanorods followed by ZnO etching. The nanotube arrays show a strong absorption edge at approximately 700 nm, high photoresponse under visible light illumination, and good visible light-driven photocatalytic capability. This nanotube array on substrate morphology provides a device like catalyst assembly without sacrificing the surface area and is very attractive due to the recycling convenience after usage, as compared to freestanding nanostructures.
This work was supported by GRF of RGC (project no. 414710), direct grant (project no. 2060438), and UGC equipment grant (SEG_CUHK06).
- Hu X, Li G, Yu J: Design, fabrication, and modification of nanostructured semiconductor materials for environmental and energy applications. Langmuir 2010, 26: 3031–3039. 10.1021/la902142bView ArticleGoogle Scholar
- Zhang H, Chen G, Bahnemann D: Photoelectrocatalytic materials for environmental applications. J Mater Chem 2009, 19: 5089–5121. 10.1039/b821991eView ArticleGoogle Scholar
- Malato S, Fernandez-Ibanez P, Maldonado M, Blanco J, Gernjak W: Decontamination and disinfection of water by solar photocatalysis: recent overview and trends. Catal Today 2009, 147: 1–59. 10.1016/j.cattod.2009.06.018View ArticleGoogle Scholar
- Gaya U, Abdullah A: Heterogeneous photocatalytic degradation of organic contaminants over titanium dioxide: a review of fundamentals, progress and problems. J Photochem Photobiol C-Photochem Rev 2008, 9: 1–12. 10.1016/j.jphotochemrev.2007.12.003View ArticleGoogle Scholar
- Hu L, Chen G: Analysis of optical absorption in silicon nanowire arrays for photovoltaic applications. Nano Lett 2007, 7: 3249–3252. 10.1021/nl071018bView ArticleGoogle Scholar
- Zhu J, Yu Z, Burkhard G, Hsu C, Connor S, Xu Y, Wang Q, McGehee M, Fan S, Cui Y: Optical absorption enhancement in amorphous silicon nanowire and nanocone arrays. Nano Lett 2009, 9: 279–282. 10.1021/nl802886yView ArticleGoogle Scholar
- Chen X, Mao S: Titanium dioxide nanomaterials: synthesis, properties, modifications, and applications. Chem Rev 2007, 107: 2891–2959. 10.1021/cr0500535View ArticleGoogle Scholar
- Fujishima A, Zhang X, Tryk D: TiO2 photocatalysis and related surface phenomena. Surf Sci Rep 2008, 63: 515–582. 10.1016/j.surfrep.2008.10.001View ArticleGoogle Scholar
- Zhang F, Wong S: Controlled synthesis of semiconducting metal sulfide nanowires. Chem Mater 2009, 21: 4541–4554. 10.1021/cm901492fView ArticleGoogle Scholar
- Costi R, Saunders A, Elmalem E, Salant A, Banin U: Visible light-induced charge retention and photocatalysis with hybrid CdSe-Au nanodumbbells. Nano Lett 2008, 8: 637–641. 10.1021/nl0730514View ArticleGoogle Scholar
- Elmalem E, Saunders A, Costi R, Salant A, Banin U: Growth of photocatalytic CdSe-Pt nanorods and nanonets. Adv Mater 2008, 20: 4312–4317. 10.1002/adma.200800044View ArticleGoogle Scholar
- Morales W, Cason M, Aina O, de Tacconi N, Rajeshwar K: Combustion synthesis and characterization of nanocrystalline WO3. J Am Chem Soc 2008, 130: 6318–6319. 10.1021/ja8012402View ArticleGoogle Scholar
- Abe R, Takami H, Murakami N, Ohtani B: Pristine simple oxides as visible light driven photocatalysts: highly efficient decomposition of organic compounds over platinum-loaded tungsten oxide. J Am Chem Soc 2008, 130: 7780–7781. 10.1021/ja800835qView ArticleGoogle Scholar
- Xiang Q, Meng G, Zhao H, Zhang Y, Li H, Ma W, Xu J: Au nanoparticle modified WO3 nanorods with their enhanced properties for photocatalysis and gas sensing. J Phys Chem C 2010, 114: 2049–2055. 10.1021/jp909742dView ArticleGoogle Scholar
- Pulgarin C, Kiwi J: Iron oxide-mediated degradation, photodegradation, and biodegradation of aminophenols. Langmuir 1995, 11: 519–526. 10.1021/la00002a026View ArticleGoogle Scholar
- Xie H, Li Y, Jin S, Han J, Zhao X: Facile fabrication of 3D-ordered macroporous nanocrystalline iron oxide films with highly efficient visible light induced photocatalytic activity. J Phys Chem C 2010, 114: 9706–9712. 10.1021/jp102525yView ArticleGoogle Scholar
- Zhou X, Yang H, Wang C, Mao X, Wang Y, Yang Y, Liu G: Visible light induced photocatalytic degradation rhodamine B on one-dimensional iron oxide particles. J Phys Chem C 2010, 114: 17051–17061. 10.1021/jp103816eView ArticleGoogle Scholar
- Cha H, Kim S, Lee K: Jung, Kang Y: Single-crystalline porous hematite nanorods: photocatalytic and magnetic properties. J Phys Chem C 2011, 115: 19129–19135. 10.1021/jp206958gView ArticleGoogle Scholar
- Zhang Y, Deng B, Zhang T, Gao D, Xu A: Shape effects of Cu2O polyhedral microcrystals on photocatalytic activity. J Phys Chem C 2010, 114: 5073–5079. 10.1021/jp9110037View ArticleGoogle Scholar
- Fu H, Pan C, Yao W, Zhu Y: Visible-light-induced degradation of rhodamine B by nanosized Bi2WO6. J Phys Chem B 2005, 109: 22432–22439. 10.1021/jp052995jView ArticleGoogle Scholar
- Fu H, Zhang S, Xu T, Zhu Y, Chen J: Photocatalytic degradation of RhB by fluorinated Bi2WO6 and distributions of the intermediate products. Environ Sci Technol 2008, 42: 2085–2091. 10.1021/es702495wView ArticleGoogle Scholar
- Li X, Hou Y, Zhao Q, Teng W, Hu X, Chen G: Capability of novel ZnFe2O4 nanotube arrays for visible-light induced degradation of 4-chlorophenol. Chemosphere 2011, 82: 581–586. 10.1016/j.chemosphere.2010.09.068View ArticleGoogle Scholar
- Zhou M, Zhu H, Wang X, Xu Y, Tao Y, Hark S, Xiao X, Li Q: CdSe nanotube arrays on ITO via aligned ZnO nanorods templating. Chem Mater 2010, 22: 64–69. 10.1021/cm902045jView ArticleGoogle Scholar
- Zhang J, Gao S, Huang B, Dai Y, Wang J, Lu J: Preparation of CdSe nanocrystals with special morphologies. Prog Chem 2010, 22: 1901–1910.Google Scholar
- Wang X, Xu Y, Zhu H, Liu R, Wang H, Li Q: Crystalline Te nanotube and Te nanorods-on-CdTe nanotube arrays on ITO via a ZnO nanorod templating-reaction. Crystengcomm 2011, 13: 2955–2959. 10.1039/c1ce00010aView ArticleGoogle Scholar
- Vayssieres L, Keis K, Lindquist S, Hagfeldt A: Purpose-built anisotropic metal oxide material: 3D highly oriented microrod array of ZnO. J Phys Chem B 2001, 105: 3350–3352. 10.1021/jp010026sView ArticleGoogle Scholar
- Vayssieres L: Growth of arrayed nanorods and nanowires of ZnO from aqueous solutions. Adv Mater 2003, 15: 464–466. 10.1002/adma.200390108View ArticleGoogle Scholar
- Greene L, Law M, Goldberger J, Kim F, Johnson J, Zhang Y, Saykally R, Yang P: Low-temperature wafer-scale production of ZnO nanowire arrays. Angew Chem Int Ed 2003, 42: 3031–3034. 10.1002/anie.200351461View ArticleGoogle Scholar
- Greene L, Yuhas B, Law M, Zitoun D, Yang P: Solution-grown zinc oxide nanowires. Inorg Chem 2006, 45: 7535–7543. 10.1021/ic0601900View ArticleGoogle Scholar
- Cocivera M, Darkowski A, Love B: Thin-film CdSe electrodeposition from selenosulfite solution. J Electrochem Soc 1984, 131: 2514–2517. 10.1149/1.2115350View ArticleGoogle Scholar
- Szabo J, Cocivera M: Composition and performance of thin-film CdSe eletrodeposited from selenosulfite solution. J Electrochem Soc 1986, 133: 1247–1252. 10.1149/1.2108828View ArticleGoogle Scholar
- Patterson A: The Scherrer formula for X-ray particle size determination. Phys Rev 1939, 56: 978–982. 10.1103/PhysRev.56.978View ArticleGoogle Scholar
- Waseda Y, Matsubara E, Shinoda K: Quantitative analysis of powder mixtures and determination of crystalline size and lattice strain. In X-ray Diffraction Crystallography: Introduction, Examples and Solved Problems. Heidelberg: Springer; 2011:121–126.View ArticleGoogle Scholar
- Moss T, Burrell G, Ellis B: Semiconductor Opto-electronics. London: Butterworths; 1973.Google Scholar
- Basu P: Theory of Optical Processes in Semiconductors: Bulk and Microstructures. Oxford: Clarendon press; 1997.Google Scholar
- Bouroushian M: Cadmium selenide (CdSe). In Electrochemistry of Metal Chalcogenides. Berlin: Springer; 2010:94–98.View ArticleGoogle Scholar
- Buhler N, Meier K, Reber J: Photochemical hydrogen-production with cadmium-sulfide suspensions. J Phys Chem 1984, 88: 3261–3268. 10.1021/j150659a025View ArticleGoogle Scholar
- Reber J, Meier K: Photochemical production of hydrogen with zinc-sulfide suspensions. J Phys Chem 1984, 88: 5903–5913. 10.1021/j150668a032View ArticleGoogle Scholar
- Sathish M, Viswanathan B, Viswanath R: Alternate synthetic strategy for the preparation of CdS nanoparticles and its exploitation for water splitting. Int J Hydrog Energy 2006, 31: 891–898. 10.1016/j.ijhydene.2005.08.002View ArticleGoogle Scholar
- Banerjee S, Mohapatra S, Das P, Misra M: Synthesis of coupled semiconductor by filling 1D TiO2 nanotubes with CdS. Chem Mater 2008, 20: 6784–6791. 10.1021/cm802282tView ArticleGoogle Scholar
- Chouhan N, Yeh C, Hu S, Liu R, Chang W, Chen K: Photocatalytic CdSe QDs-decorated ZnO nanotubes: an effective photoelectrode for splitting water. Chem Commun 2011, 47: 3493–3495. 10.1039/c0cc05548dView ArticleGoogle Scholar
- Ollis D: Contaminant degradation in water. Environ Sci Technol 1985, 19: 480–484. 10.1021/es00136a002View ArticleGoogle Scholar
- Takizawa T, Watanabe T, Honda K: Photocatalysis through excitation of absorbates. 2. a comparative-study of rhodamineB and methylene blue on cadmium sulfide. J Phys Chem 1978, 82: 1391–1396. 10.1021/j100501a014View ArticleGoogle Scholar
- Mills A, LeHunte S: An overview of semiconductor photocatalysis. J Photochem Photobiol A-Chem 1997, 108: 1–35. 10.1016/S1010-6030(97)00118-4View ArticleGoogle Scholar
- Walukiewicz W: Intrinsic limitations to the doping of wide-gap semiconductors. Physica B 2001, 302: 123–134.View ArticleGoogle Scholar
- Chen X, Shen S, Guo L, Mao S: Semiconductor-based photocatalytic hydrogen generation. Chem Rev 2010, 110: 6503–6570. 10.1021/cr1001645View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.