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Electrochemical synthesis of TiO2 nanotubes and its anodic dopping

Grant number: 12/06778-0
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): June 01, 2012
Effective date (End): May 31, 2013
Field of knowledge:Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
Principal researcher:Renato Garcia de Freitas Sobrinho
Grantee:Milli Aline Sant Anna
Home Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

The production of nanostructured electrochemical devices and energy converters has shown significant results, due to its intrinsic properties of low dimensionality. The nature of the semiconductor TiO2 nanotubes makes it a promising candidate for electrolysis of water, energy converter device, and photocatalytic self-cleaning applications. Therefore, this project proposes to evaluate the electrochemical formation of TiO2-nanotubes (TiO2NT) and their application as photo-electrodes for water splitting. The manufacture of TiO2NT was first reported by Zwilling et al. in 1999. The first generation of TiO2NT synthesized using an electrochemical route was limited to nanotubes with short lengths of up to 600nm. The second generation of TiO2NT, in which aqueous electrolytes were replaced by organic medium, led to new morphologies. In this sense, the use of glycerol allowed to obtain the TiO2NT with walls of low roughness and length of about 7.0 micrometers. Finally, the third generation of TiO2NT materials was obtained in an ionic liquids medium and these resulted in TiO2NT with double walls. TiO2 nanotubes present as the main crystalline phases a mixture of rutile and anatase phases. Several factors influenced the morphology and microstructure, such as pH and electrolyte composition, the concentration of F-, the existence of convective flow in the solution, the initial state of the metal to be anodized, anodizing temperature, voltage (when anodizing at constant potential), the water content in the electrolyte, temperature, and atmosphere of heat treatment after the electrochemical synthesis. The efficiency of photo-electrocatalytic TiO2NT is associated with the recombination rate of e-/h+ once the photocurrent magnitude is related to the efficiency of the transport agent through the base of the nanotubes, and h+ on the TiO2-electrolyte interface. Thus, thick-walled nanotubes had lower rates of recombination and e-/h+ and, consequently, an increase in photocatalytic activity. Moreover, TiO2NT with larger diameters allows better diffusion of small organic molecules inside the tubes to be eletrooxidized. Thus, the major objective of this project is to understand the mechanistic processes, which directly affect the phenomena related to water splitting.(AU)

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Scientific publications (4)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
FREITAS, R. G.; SANTANNA, M. A.; PEREIRA, E. C.. Preparation and Characterization of TiO2 Nanotube Arrays in Ionic Liquid for Water Splitting. Electrochimica Acta, v. 136, p. 404-411, . (10/05555-2, 12/06778-0)
FREITAS, R. G.; SANTANNA, M. A.; PEREIRA, E. C.. Dependence of TiO2 nanotube microstructural and electronic properties on water splitting. Journal of Power Sources, v. 251, p. 178-186, . (10/05555-2, 12/06778-0)
SANTANNA, M. A.; MENEZES, W. T.; SANTANA, Y. V. B.; FERRER, M. M.; GOUVEIA, A. F.; FACETO, A. D.; TEREZO, A. J.; OLIVEIRA, A. J. A.; LONGO, E.; FREITAS, R. G.; et al. The effect of TiO2 nanotube morphological engineering and ZnS quantum dots on the water splitting reaction: A theoretical and experimental study. INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, v. 43, n. 14, p. 6838-6850, . (12/06778-0, 12/22823-6, 10/05555-2)
FREITAS, R. G.; LUCAS, F. W. S.; SANTANNA, M. A.; MENDES, R. A.; TEREZO, A. J.; DE SOUZA, G. L. C.; MASCARO, L. H.; PEREIRA, E. C.. An experimental and theoretical study on the electronic and structural properties of CdSe@TiO2 nanotube arrays. Physical Chemistry Chemical Physics, v. 18, n. 38, p. 26885-26893, . (10/05555-2, 12/06778-0, 12/10947-2)

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