Abstract

Efficient capture of solar energy by semiconductors to produce hydrogen by splitting water molecules is one of the most important challenges of Energy Sciences. A sustainable economy based on hydrogen requires produce this fuel by using renewable energy sources. In this context, the decomposition of water with sunlight becomes a very interesting concept due both are renewable, abundant and inexpensive sources. This process named photolysis uses a semiconductor material (photocatalyst) as its main element. At the present there is not a photocatalyst efficient enough to present a viable alternative, so it is necessary to conduct thorough researches to make significant progress. Currently available photocatalysts are suitable for water splitting using the ultraviolet portion of the spectrum, missing the visible light less energetic but more abundant. Therefore any viable future photolysis technology should be capable of utilizing a substantial fraction of the visible spectrum. Since the discovery of sunlight-assisted electrolysis of water using TiO2 photoelectrodes in 1972, there is a great interest in using metal oxides for photolysis. Several other metal oxides have been identified to sustain photolysis of water, even though titania still dominates as the oxide of choice for photocatalysis. Recently, impressive progress has been made creating oxides in the form of nanostructures with large surface areas to promote light harvesting. In particular TiO2-XCX nanotube arrays were reported to show efficient water splitting and much higher photocurrent densities than pure TiO2 nanotube arrays under visible-light illumination. The aim of this proposal consists to create an efficient photocatalyst based on nanostructured arrays. Will focus our efforts on making a hybrid nanostructure of titanium oxide and carbon nanotubes supported by an alumina membrane (TiO2/TiO2-XCX /CNTs/AAO). The idea behind using CNTs is drain quickly the photogenerated electrons in order to prevent the electron-hole recombination in the semiconductor. Also we will explore the fabrication of multilayer nanotube arrays where tubes are formed by hematite and CNTs. Our approach consider carryout a systematic study to find the optimal structural and composition parameters to achieve efficient splitting of water. The key is to grow the materials in a finely tunable nano-architecture. The hybrid nanostructured arrays will be fabricated by several deposition techniques using porous alumina membranes as a template. One of the major advantages in using this nanoporous structures, is the low cost of produce a large area template with well-controlled properties down to nanometer. With this technique we will be able to produce the hybrid nanostructured arrays with the necessary degree of control and a relatively low cost. We expect that these arrays of multilayered nanotubes behave as an efficient photocatalyst using a substantial fraction of the visible spectrum.