Publication Details (including relevant citation information):
ACS Nano, 2011, 5 (6), pp 5056–5066
In recent years, considerable efforts have been made to design and discover photoactive nanostructured materials that can be used as anodes in water photoelectrolysis cells. Herein, we report on the growth of a novel photoanode material composed of self-ordered, vertically oriented nanotube arrays of titanium–palladium mixed oxynitride films via anodization of Ti–Pd alloy in an electrolyte solution of formamide containing NH4F at room temperature, followed by annealing in an ammonia atmosphere. The nanostructure topology was found to depend on both the anodization time and the applied voltage. Our results demonstrate the ability to grow mixed oxynitride nanotube array films that are several micrometers thick. The Ti–Pd oxynitride nanotube array films were utilized in solar-spectrum water photoelectrolysis, demonstrating a photocurrent density of 1.9 mA/cm2 and a 5-fold increase in the photoconversion efficiency under AM 1.5 illumination (100 mW/cm2, 1.0 M KOH) compared to pure TiO2 nanotubes fabricated and tested under the same conditions. The obtained efficiency is among the highest reported values for a TiO2 nanotube-based photoelectrochemical cell. This enhancement in the photoconversion efficiency is related to the synergistic effects of Pd alloying, nitrogen doping, and the unique structural properties of the fabricated nanotube arrays.