1. Vertically Oriented Ti−Fe−O Nanotube Array Films: Toward a Useful Material Architecture for Solar Spectrum Water Photoelectrolysis
- Author
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Haripriya E. Prakasam, Craig A. Grimes, Oomman K. Varghese, Gopal K. Mor, and Karthik Shankar
- Subjects
Nanotube ,Materials science ,Macromolecular Substances ,Photochemistry ,Surface Properties ,Iron ,Molecular Conformation ,Oxide ,chemistry.chemical_element ,Bioengineering ,Nanotechnology ,Electrolysis ,chemistry.chemical_compound ,Materials Testing ,Solar Energy ,General Materials Science ,Particle Size ,Titanium ,Nanotubes ,Anodizing ,Mechanical Engineering ,Water ,Membranes, Artificial ,General Chemistry ,Condensed Matter Physics ,Amorphous solid ,Oxygen ,chemistry ,Chemical engineering ,Photoelectrolysis ,Water splitting ,Crystallization ,Hydrogen ,Visible spectrum - Abstract
In an effort to obtain a material architecture suitable for high-efficiency visible spectrum water photoelectrolysis, herein we report on the fabrication and visible spectrum (380-650 nm) photoelectrochemical properties of self-aligned, vertically oriented Ti-Fe-O nanotube array films. Ti-Fe metal films of variable composition, iron content ranging from 69% to 3.5%, co-sputtered onto FTO-coated glass are anodized in an ethylene glycol + NH4F electrolyte. The resulting amorphous samples are annealed in oxygen at 500 degrees C, resulting in nanotubes composed of a mixed Ti-Fe-O oxide. Some of the iron goes into the titanium lattice substituting titanium ions, and the rest either forms alpha-Fe2O3 crystallites or remains in the amorphous state. Depending upon the Fe content, the band gap of the resulting films ranges from about 380 to 570 nm. The Ti-Fe oxide nanotube array films are utilized in solar spectrum water photoelectrolysis, demonstrating 2 mA/cm2 under AM 1.5 illumination with a sustained, time-energy normalized hydrogen evolution rate by water splitting of 7.1 mL/W.hr in a 1 M KOH solution with a platinum counter electrode under an applied bias of 0.7 V. The surface morphology, structure, elemental analysis, optical, and photoelectrochemical properties of the Ti-Fe oxide nanotube array films are considered.
- Published
- 2007