Large-scale preparation of nanoporous TiO2 film on titanium substrate with improved photoelectrochemical performance
© Tan et al.; licensee Springer. 2014
Received: 13 March 2014
Accepted: 12 April 2014
Published: 24 April 2014
Fabrication of three-dimensional TiO2 films on Ti substrates is one important strategy to obtain efficient electrodes for energy conversion and environmental applications. In this work, we found that hierarchical porous TiO2 film can be prepared by treating H2O2 pre-oxidized Ti substrate in TiCl3 solution followed by calcinations. The formation process is a combination of the corrosion of Ti substrate and the oxidation hydrolysis of TiCl3. According to the characterizations by scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflectance spectroscopy (DRS), the anatase phase TiO2 films show porous morphology with the smallest diameter of 20 nm and possess enhanced optical absorption properties. Using the porous film as a working electrode, we found that it displays efficient activity for photoelectrocatalytic decolorization of rhodamine B (RhB) and photocurrent generation, with a photocurrent density as high as 1.2 mA/cm2. It represents a potential method to fabricate large-area nanoporous TiO2 film on Ti substrate due to the scalability of such chemical oxidation process.
In recent years, TiO2 has been widely studied and applied in diverse fields, such as photocatalysis, dye-sensitized solar cell, self-cleaning surface, sensor, and biomedicine [1–6]. It is well known that TiO2 nanoparticles have the potential to remove recalcitrant organic pollutants in wastewater. However, it is prerequisite to produce immobilized TiO2 photocatalysts with highly efficient activity by scale-up methods. Recently, considerable efforts have been taken to use metallic titanium as the precursor to develop three-dimensional TiO2 films with controllable ordered morphologies, such as nanotubes , nanorods , nanowires , and nanopores . The in situ-generated TiO2 films over titanium substrates possess such advantages as stable with low carbon residual, excellent mechanical strength, and well electron conductivity, which make them suitable to be used as electrodes for photoelectrochemical-related applications [6, 11]. Although a well-defined structural nanotube or nanoporous TiO2 film on metallic Ti can be synthesized by an anodic method [6, 7, 10–13], it is still a big challenge to scale up the production of such TiO2 film due to the limitation of electrochemical reactor and the high energy consumption. Chemical oxidation methods by treating titanium substrates in oxidation solutions are more scalable for various applications. By soaking titanium substrates in H2O2 solution followed with calcinations, titania nanorod or nanoflower films can be obtained [8, 14]. However, the film always displays discontinuous structure with many cracks, and its thickness is less than 1 μm [8, 15]. Both of these would result in a low photoelectrochemical performance. With the addition of concentrated NaOH in the H2O2 solution, a porous nanowire TiO2 film can be achieved after an ionic exchange with protons and subsequent calcinations . Employing NaOH and organic solvent as the oxidation solution and elevating the treating temperature, Ti substrate would completely transform into free-standing TiO2 nanowire membranes . However, the disappearance of Ti substrate makes this membrane impossible to serve as an electrode.
Compared to titanium alkoxides or TiCl4, there are much fewer reports on the synthesis of TiO2 nanostructure with the precursor of TiCl3. Normally, anatase TiO2 film can be fabricated via the anodic oxidation hydrolysis of TiCl3 solution [17, 18]. Recently, Hosono et al. synthesized rectangular parallelepiped rutile TiO2 films by hydrothermally treating TiCl3 solution with the addition of a high concentration of NaCl , and Feng et al. developed TiO2 nanorod films with switchable superhydrophobicity/superhydrophilicity transition properties via a similar method . Moreover, a hierarchically branched TiO2 nanorod film with efficient photon-to-current conversion efficiency can be achieved by treating the nanorod TiO2 film in TiCl3 solution . However, all of these nanostructural TiO2 films from TiCl3 solution were grown over glass or alumina substrates. Fabricating nanostructral TiO2 films over metallic Ti substrates is a promising way to providing high-performance photoresponsible electrodes for photoelectrochemical applications. The obstacle for starting from Ti substrates and TiCl3 solution must be the corrosion of metallic Ti at high temperatures in the HCl solution, which is one of the components in TiCl3 solution. However, the corrosion could also be controlled and utilized for the formation of porous structures. According to reports, the general method to prepare nanoporous TiO2 film on Ti substrate is through anodic oxidation and post-sonication [10, 12]. In this contribution, we proposed a facile way to fabricate nanoporous TiO2 films by post-treating the H2O2-oxidized TiO2 film in a TiCl3 solution. The as-prepared nanoporous TiO2 film display homogeneous porous structure with enhanced optical adsorption property and photoelectrocatalytic performance, which indicates that the film is promising in the applications of water purification and photoelectrochemical devices.
Cleansed Ti plates (99.5% in purity, Baoji Ronghao Ti Co. Ltd., Shanxi, China) with sizes of 1.5 × 1.5 cm2 were pickled in a 5 wt% oxalic acid solution at 100°C for 2 h, followed by rinsing with deionized water and drying in an air stream. The nanoporous TiO2 film was prepared by a two-step oxidation procedure. Briefly, the pretreated Ti plate was firstly soaked in a 15 mL 20 wt% H2O2 solution in a tightly closed bottle, which was maintained at 80°C for 12 h. The treated Ti plate was rinsed gently with deionized water and dried. Then, it was immersed in a 10 mL TiCl3 solution (0.15 wt%) at 80°C for 2 h. Finally, the film was cleaned, dried, and calcined at 450°C for 2 h. The obtained nanoporous TiO2 film was designed as NP-TiO2. Two control samples were synthesized, including the one designed as TiO2-1, which was obtained by directly calcining the cleansed Ti plate, and the other named as TiO2-2, which was prepared by one-step treatment of the Ti plate in a TiCl3 solution.
The surface morphology of TiO2 films was observed using a field emission scanning electron microscope (SEM; Zeiss Ultra 55, Oberkochen, Germany). The crystal phases were analyzed using a powder X-ray diffractometer (XRD; D8 Advance, Bruker, Ettlingen, Germany) with Cu Kα radiation, operated at 40 kV and 36 mA (λ = 0.154056 nm). UV-vis diffuse reflectance spectra (DRS) were recorded on a Lambda 950 UV/Vis spectrophotometer (PerkinElmer Instrument Co. Ltd., Waltham, MA, USA) and converted from reflection to absorption by the Kubelka-Munk method.
Photoelectrochemical test systems were composed of a CHI 600D electrochemistry potentiostat, a 500-W xenon lamp, and a homemade three-electrode cell using as-prepared TiO2 films, platinum wire, and a Ag/AgCl as the working electrode, counter electrode, and reference electrode, respectively. A 0.5 M Na2SO4 solution purged with nitrogen was used as electrolyte for all of the measurements.
The photocatalytic or photoelectrocatalytic degradation of rhodamine B (RhB) over the NP-TiO2 film was carried out in a quartz glass cuvette containing 20 mL of RhB solution (C28H31ClN2O3, initial concentration 5 mg/L). The pH of the solution was buffered to 7.0 by 0.1 M phosphate. The solution was stirred continuously by a magnetic stirrer. Photoelectrocatalytic reaction was performed in a three-electrode system with a 0.5-V anodic bias. The exposed area of the electrodes under illumination was 1.5 cm2. Concentration of RhB was measured by spectrometer at the wavelength of 554 nm.
Results and discussion
A nanoporous TiO2 film on Ti substrate was synthesized by treating the initially H2O2-oxidized Ti plate in hot TiCl3 solution and followed by calcinations. The pre-oxidation in H2O2 solution is necessary to form such porous structure, indicating that the formation process is a combination of the corrosion of Ti substrate and the oxidation hydrolysis of TiCl3. The film possesses exclusively anatase phase and hierarchical porous morphology, with the diameter of the inside pores as small as 20 nm. The porous TiO2 film displays enhanced optical absorption, photocurrent generation, and efficient photoelectrocatalytic activity for RhB decolorization. The generated photocurrent density can reach as high as 1.2 mA/cm2. The chemical oxidation method for the nanoporous TiO2 film is possible to be scaled up and developed into a strategy to provide efficient TiO2 electrodes for diverse applications.
This work is financially supported by the Natural Science Foundation of China (No. 21377084) and Shanghai Municipal Natural Science Foundation (No. 13ZR1421000). We gratefully acknowledge the support in DRS measurements and valuable suggestions by Ms. Xiaofang Hu of the School of Environmental Science and Engineering, Shanghai Jiao Tong University.
- Fujishima A, Zhang X, Tryk DA: TiO2 photocatalysis and related surface phenomena. Surf Sci Rep 2008, 63: 515–582. 10.1016/j.surfrep.2008.10.001View ArticleGoogle Scholar
- Tran PD, Wong LH, Barber J, Loo JSC: Recent advances in hybrid photocatalysts for solar fuel production. Energ Environ Sci 2012, 5: 5902. 10.1039/c2ee02849bView ArticleGoogle Scholar
- Kubacka A, Fernandez-Garcia M, Colon G: Advanced nanoarchitectures for solar photocatalytic applications. Chem Rev 2012, 112: 1555–1614. 10.1021/cr100454nView ArticleGoogle Scholar
- Long MC, Wu D, Cai WM: Photoinduced hydrophilic effect and its application on self-cleaning technology. Recent Pat Eng 2010, 4: 189–199. 10.2174/187221210794578619View ArticleGoogle Scholar
- Cheyne R, Smith T, Trembleau L, McLaughlin A: Synthesis and characterisation of biologically compatible TiO2 nanoparticles. Nanoscale Res Lett 2011, 6: 1–6.View ArticleGoogle Scholar
- Zheng Q, Zhou BX, Bai J, Li LH, Jin ZJ, Zhang JL, Li JH, Liu YB, Cai WM, Zhu XY: Self-organized TiO2 nanotube array sensor for the determination of chemical oxygen demand. Adv Mater 2008, 20: 1044–1049. 10.1002/adma.200701619View ArticleGoogle Scholar
- Macak JM, Tsuchiya H, Taveira L, Aldabergerova S, Schmuki P: Smooth anodic TiO2 nanotubes. Angew Chem Int Ed 2005, 44: 7463–7465. 10.1002/anie.200502781View ArticleGoogle Scholar
- Wu JM, Zhang TW, Zeng YW, Hayakawa S, Tsuru K, Osaka A: Large-scale preparation of ordered titania nanorods with enhanced photocatalytic activity. Langmuir 2005, 21: 6995–7002. 10.1021/la0500272View ArticleGoogle Scholar
- Wu YH, Long MC, Cai WM, Dai SD, Chen C, Wu DY, Bai J: Preparation of photocatalytic anatase nanowire films by in situ oxidation of titanium plate. Nanotechnology 2009, 20: 185703. 10.1088/0957-4484/20/18/185703View ArticleGoogle Scholar
- de Tacconi NR, Chenthamarakshan CR, Yogeeswaran G, Watcharenwong A, de Zoysa RS, Basit NA, Rajeshwar K: Nanoporous TiO2 and WO3 films by anodization of titanium and tungsten substrates: influence of process variables on morphology and photoelectrochemical response†. J Phys Chem B 2006, 110: 25347–25355. 10.1021/jp064527vView ArticleGoogle Scholar
- Quan X, Yang SG, Ruan XL, Zhao HM: Preparation of titania nanotubes and their environmental applications as electrode. Environ Sci Technol 2005, 39: 3770–3775. 10.1021/es048684oView ArticleGoogle Scholar
- Liu YB, Zhou BX, Bai J, Li JH, Zhang JL, Zheng Q, Zhu X, Cai WM: Efficient photochemical water splitting and organic pollutant degradation by highly ordered TiO2 nanopore arrays. Appl Catal B Environ 2009, 89: 142–148. 10.1016/j.apcatb.2008.11.034View ArticleGoogle Scholar
- Xu C, Song Y, Lu LF, Cheng CW, Liu DF, Fang XH, Chen XY, Zhu XF, Li DD: Electrochemically hydrogenated TiO2 nanotubes with improved photoelectrochemical water splitting performance. Nanoscale Res Lett 2013, 8: 7. 10.1186/1556-276X-8-7View ArticleGoogle Scholar
- Wu JM, Huang B, Zeng YH: Low-temperature deposition of anatase thin films on titanium substrates and their abilities to photodegrade rhodamine B in water. Thin Solid Films 2006, 497: 292–298. 10.1016/j.tsf.2005.10.066View ArticleGoogle Scholar
- Wu YH, Long MC, Cai WM: Novel synthesis and property of TiO2 nano film photocatalyst with mixed phases. J Chem Eng Chin Univ 2010, 24: 1005–1010.Google Scholar
- Hu A, Zhang X, Oakes KD, Peng P, Zhou YN, Servos MR: Hydrothermal growth of free standing TiO2 nanowire membranes for photocatalytic degradation of pharmaceuticals. J Hazard Mater 2011, 189: 278–285. 10.1016/j.jhazmat.2011.02.033View ArticleGoogle Scholar
- Kavan L, O’Regan B, Kay A, Grätzel M: Preparation of TiO2 (anatase) films on electrodes by anodic oxidative hydrolysis of TiCl3. J Electroanal Chem 1993, 346: 291–307. 10.1016/0022-0728(93)85020-HView ArticleGoogle Scholar
- Lei Y, Zhang LD, Fan JC: Fabrication, characterization and Raman study of TiO2 nanowire arrays prepared by anodic oxidative hydrolysis of TiCl3. Chem Phys Lett 2001, 338: 231–236. 10.1016/S0009-2614(01)00263-9View ArticleGoogle Scholar
- Hosono E, Fujihara S, Kakiuchi K, Imai H: Growth of submicrometer-scale rectangular parallelepiped rutile TiO2 films in aqueous TiCl3 solutions under hydrothermal conditions. J Am Chem Soc 2004, 126: 7790–7791. 10.1021/ja048820pView ArticleGoogle Scholar
- Feng XJ, Zhai J, Jiang L: The fabrication and switchable superhydrophobicity of TiO2 nanorod films. Angew Chem Int Ed 2005, 44: 5115–5118. 10.1002/anie.200501337View ArticleGoogle Scholar
- Cho IS, Chen Z, Forman AJ, Kim DR, Rao PM, Jaramillo TF, Zheng X: Branched TiO2 nanorods for photoelectrochemical hydrogen production. Nano Lett 2011, 11: 4978–4984. 10.1021/nl2029392View ArticleGoogle Scholar
- Lin J, Liu K, Chen X: Synthesis of periodically structured titania nanotube films and their potential for photonic applications. Small 2011, 7: 1784–1789. 10.1002/smll.201002098View ArticleGoogle Scholar
- Lu Y, Yu H, Chen S, Quan X, Zhao H: Integrating plasmonic nanoparticles with TiO photonic crystal for enhancement of visible-light-driven photocatalysis. Environ Sci Technol 2012, 46: 1724–1730. 10.1021/es202669yView ArticleGoogle Scholar
- Peter LM: Dynamic Aspects of Semiconductor Photoelectrochemistry. Chem Rev 1990, 90: 753–769. 10.1021/cr00103a005View ArticleGoogle Scholar
- Long MC, Beranek R, Cai WM, Kisch H: Hybrid semiconductor electrodes for light-driven photoelectrochemical switches. Electrochim Acta 2008, 53: 4621–4626. 10.1016/j.electacta.2008.01.077View ArticleGoogle Scholar
- Abrantes LM, Peter LM: Transient photocurrents at passive iron electrodes. J Electroanal Chem Interfacial Electrochem 1983, 150: 593–601. 10.1016/S0022-0728(83)80238-1View ArticleGoogle Scholar
- Brusa MA, Grela MA: Experimental upper bound on phosphate radical production in TiO2 photocatalytic transformations in the presence of phosphate ions. Phys Chem Chem Phys 2003, 5: 3294. 10.1039/b302296jView ArticleGoogle Scholar
- Jiang DL, Zhang SQ, Zhao HJ: Photocatalytic degradation characteristics of different organic compounds at TiO2 Nanoporous film electrodes with mixed anatase/rutile phases. Environ Sci Technol 2007, 41: 303–308. 10.1021/es061509iView ArticleGoogle Scholar
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