Synthesis and Photoelectrochemical Properties of Anodic Oxide Films on Titanium Formed by Pulse Anodization

Abstract

Nanostructured titanium oxide represents one of the most important semiconductors suitable for a variety of technological applications. TiO2 nanopore arrays were fabricated by pulse anodization of titanium foil under specific alternating-voltage conditions. The anodic titanium oxide layer (ATO) with a structural modulation of pores was formed by a two-step electrochemical anodization at 20°C. The titanium foil was pre-textured at the cell potential of 60 V in an ethylene glycol solution containing NH4F (0.38 wt%) and H2O (1.79 wt%). After the first anodization, the oxide layer was removed, and the sample was re-anodized using different sequences of potential pulses. The morphology, structure and photoelectrochemical properties of the fabricated nanoporous TiO2 were characterized in detail. It was established that too high or too long potential pulses result in separation of individual stacked layers. Moreover, the nanoporous surface morphology of oxide can be destroyed by a lengthy pulse anodization process. These results indicated that strict control of pulse anodization conditions and a number of anodizing cycles are essential to fabricate ATO layers with a modulated nanopore shape. The bamboo-like ATO layers formed by pulse voltage anodizing exhibited enhanced photoelectrochemical properties when compared to the oxide layer formed at the constant voltage conditions.