(Invited) Novel Anodic Oxide Nanotube Array Architectures for Solar Photoelectrochemical Fuel Generation

Abstract

Electrochemical anodization has progressed from its level as a low-cost commercial technique to fabricate corrosion and abrasion resistant compact oxide coatings to the status of an effective method for growing a variety of oxide nano-architectures, particularly nanorods, nanowires, nanotubes, nanoporous films, and nanoflowers. Among these structures, self-organized vertically aligned nanotubes of oxide semiconductors have been demonstrated to possess interesting electrical, optical and mechanical properties. As in the case of most low dimensional materials, these structures also possess high surface area. Nevertheless, their unique properties applicable to solar energy conversion processes such as photoelectrochemical (PEC) fuel generation arise primarily from their vertical orientation, their ability to keep the charge carriers always in the vicinity of the surface and the pathways they offer for facile charge transport. They can form heterostructures with other low dimensional materials and function synergistically to enhance the efficiency of the PEC processes. Anodic nanotube arrays of only a few oxide semiconductors have been discovered so far; however, expanding the list further has been proven difficult. Recently, we have developed a few novel nanotubular semiconductors promising for PEC fuel generation. This presentation provides the details of their fabrication process and performance as photocatalysts for solar fuel generation.