Two novel hierarchical homogeneous nanoarchitectures of TiO2 nanorods branched and P25-coated TiO2 nanotube arrays and their photocurrent performances

Nanoscale Research Letters, Dec 2011

We report here for the first time the synthesis of two novel hierarchical homogeneous nanoarchitectures of TiO2 nanorods branched TiO2 nanotube arrays (BTs) and P25-coated TiO2 nanotube arrays (PCTs) using two-step method including electrochemical anodization and hydrothermal modification process. Then the photocurrent densities versus applied potentials of BTs, PCTs, and pure TiO2 nanotube arrays (TNTAs) were investigated as well. Interestingly, at -0.11 V and under the same illumination condition, the photocurrent densities of BTs and PCTs show more than 1.5 and 1 times higher than that of pure TNTAs, respectively, which can be mainly attributed to significant improvement of the light-absorbing and charge-harvesting efficiency resulting from both larger and rougher surface areas of BTs and PCTs. Furthermore, these dramatic improvements suggest that BTs and PCTs will achieve better photoelectric conversion efficiency and become the promising candidates for applications in DSSCs, sensors, and photocatalysis.

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Two novel hierarchical homogeneous nanoarchitectures of TiO2 nanorods branched and P25-coated TiO2 nanotube arrays and their photocurrent performances

Anzheng Hu 0 1 Cuixia Cheng 0 Xin Li 0 Jian Jiang 0 Ruimin Ding 0 Jianhui Zhu 0 Fei Wu 0 Jinping Liu 0 Xintang Huang 0 0 Institute of Nanoscience and Nanotechnology, Central China Normal University , Wuhan 430079, P. R. China 1 School of Physics and Electronic Engineering, Xiangfan University , Xiangfan 441053, Hubei, P. R. China We report here for the first time the synthesis of two novel hierarchical homogeneous nanoarchitectures of TiO2 nanorods branched TiO2 nanotube arrays (BTs) and P25-coated TiO2 nanotube arrays (PCTs) using two-step method including electrochemical anodization and hydrothermal modification process. Then the photocurrent densities versus applied potentials of BTs, PCTs, and pure TiO2 nanotube arrays (TNTAs) were investigated as well. Interestingly, at -0.11 V and under the same illumination condition, the photocurrent densities of BTs and PCTs show more than 1.5 and 1 times higher than that of pure TNTAs, respectively, which can be mainly attributed to significant improvement of the light-absorbing and charge-harvesting efficiency resulting from both larger and rougher surface areas of BTs and PCTs. Furthermore, these dramatic improvements suggest that BTs and PCTs will achieve better photoelectric conversion efficiency and become the promising candidates for applications in DSSCs, sensors, and photocatalysis. - Introduction In current years, one-dimensional (1D) TiO2 nanostructure materials, especially nanotubular [1-3] and hierarchical [4-7] nanoarchitecture TiO2 nanotube arrays (TNTAs), have initiated increasing research interest owing to their intriguing architectures because they possess very high specific surface areas and a dual-channel for the benefit of the electrons transportation from interfaces to electrodes [7-13]. These nanostructure materials have shown very promising applications in dye-sensitized solar cells (DSSCs) [14-16], photocatalysis [17-19], photosplitting water [20,21], sensors [22,23], photoelectrochemical cells [24], and piezoelectronics [25]. However, as far as we are concerned, tremendous efforts have been conducted to improve the geometrical factors of the nanotube layers [8-13,26], to convert amorphous TiO2 nanotubes into different crystalline forms (i.e., anatase or rutile phase, or mixture phases of anatase and rutile) through high temperature annealing for high performance applications [27-29], and also many studies have devoted ones mind to change the crystal structure or chemistry composition of the tubes by modifying and doping [30-33]. There still remain many challenges to prepare and discuss the homogeneous modification of TNTAs, although the similar synthesis method of growing branched ZnO nanowires [34] and the decoration process of growing TiO2 nanoparticles on TiO2 nanotubes by a TiCl4 treatment [35] have been reported. Therefore, it is particularly valuable to seek some facile and high-efficiency method to synthesize the modification of TNTAs nanostructures for further specific surface area. In this communication, we report for the first time the synthesis of two novel hierarchical homogeneous modification nanoarchitectures (i.e., P25-coated TNTAs, PCTs; and TiO2 nanorods branched TNTAs, BTs) via two-step method of electrochemical anodization and hydrothermal modification approach. The main precursors of modification are the P25 (Degussa, Germany) and titanium(IV) isopropoxide (TTIP of 95%). Erenow, the optimized nanoarchitecture TNTAs (with bigger pore diameter, longer length, and larger space among tubes) have been prepared by electrochemical anodization method. Interestingly, the as-synthesized BTs and PCTs with beautiful morphologies show both larger and rougher surface area, and these properties result in dramatic improvement of light-absorbing and charge-harvesting efficiency, which has been shown through the UV-Vis diffuse reflectance spectroscopic spectra and photoelectrochemical performances in this article. Experimental section Fabrication of optimum nanoarchitecture TNTAs In this article, TNTAs were prepared using a typical anodization approach [13]. Briefly, the fabrication process of the optimum nanoarchitecture TNTAs with bigger pore diameter, larger space among tubes and longer length was described as follows, Titanium foil samples, about 200 m 2 cm 3.5 cm (Purity99.6%, from ShengXin non-ferrous metal Co., LTD, Baoji, Shanxi, China) were cleaned with soap, acetone, and isopropanol before anodization. A two-electrode configuration was used for anodization, with Ti foil as the anode, and platinum foil as the cathode. A 99.7% pure Ti foil (0.2 mm thickness, 2 3 cm2) was immersed in the electrolyte containing 0.35 wt% NH4F (85% Lactic Acid) and 10 vol.% DMSO (dimethyl sulphoxide: purity 99.0%) at a 45 V constant potential for 9 h. Thus we obtained the amorphous TNTAs, and then the as-prepared TNTAs were annealed at 400C for 1.5 h for further use. Synthesis of hierarchical homogeneous nanoarchitecture BTs The BTs were obt (...truncated)


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Anzheng Hu, Cuixia Cheng, Xin Li, Jian Jiang, Ruimin Ding, Jianhui Zhu, Fei Wu, Jinping Liu, Xintang Huang. Two novel hierarchical homogeneous nanoarchitectures of TiO2 nanorods branched and P25-coated TiO2 nanotube arrays and their photocurrent performances, Nanoscale Research Letters, 2011, pp. 91, Volume 6, Issue 1, DOI: 10.1186/1556-276X-6-91