Abstract

Finding a source of clean and sustainable energy is one of the most important issues of society today. A potential alternative could be the use of sun light to generate hydrogen by dividing the water molecules. This process named photolysis uses semiconductor material (photocatalyst) as its main element. At the present this process is not efficient enough to present a viable alternative, and so its efficiency must be increased and costs reduced. 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 oxides for photolysis. Several other 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 recently reported to show efficient water splitting and much higher photocurrent densities than pure TiO2 nanotube arrays under visible-light illumination. The main goal of this proposal is to create an oxide based hybrid nanostructures array which could be used as an efficient photocatalyst. We will focus our efforts on making a hybrid nanostructure of titanium oxides and carbon nanotubes (TiOx-CNTs). Our approach is realized 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 nanoestructurates arrays will be fabricated by chemical vapor deposition using porous alumina membranes as a template. One of the major challenges in using this nanoporous structure is the cost efficient synthesis of the large area nanoporous arrays with well-controlled properties down to nanometer. Our approach will be growing these membranes directly over a substrate. With these experimental techniques we will be able to produce the hybrid nanostructures arrays with the necessary degree of control.