Effect of electrolytes on anodic oxidation of titanium for fabricating titanium dioxide photocatalyst

Anodic oxidation has recently been investigated for fabricating photocatalytic TiO2 layers on Ti substrates. However, the most effective electrolyte for obtaining a high-performance photocatalyst has not yet been determined. In this work, TiO2 layers were produced by anodizing a Ti substrate in electrolytes consisting of (NH4)2SO4, (NH4)3PO4, or (NH4)2O · 5B2O3, and their characteristics and photocatalytic activities were analyzed in detail. The choice of the electrolyte affected both the surface morphology and the crystallinity of the fabricated oxide layer. The incorporation of S, B, and P from the electrolytes into the oxide layers was identified, which was linked to the degree of crystallization. A methylene blue degradation test revealed that all the oxide layers fabricated in the present study could act as photocatalysts; however, their performances were different depending on the electrolyte used. This can be explained in terms of the difference in the crystallinity due to the influence of the incorporation of the various elements.

► TiO2 layers were produced by anodizing a Ti substrate in three types of electrolytes.
► The electrolyte affected the surface morphology and the crystallinity of the layer.
► The incorporation of anions was linked to the degree of crystallization.
► The photocatalytic activities were different depending on the electrolyte used.