Photocatalytic Activities and Crystal Structures of Titanium Dioxide by Anodization: Their Dependence upon Current Density

Abstract

The crystal structure, crystallinity and surface area of anodized TiO₂ were systematically investigated focusing on the current density in the anodization. Anatase phase was evolved with an increase of the current density for the anodic oxides prepared in the electrolyte of 0.1 mol·L⁻¹ sulfuric acid, and the surface area was almost constant against the current density. On the other hand, rutile phase was evolved with the same of 1.2 mol·L⁻¹ sulfuric acid, and the surface area increased with the current density. Photocatalytic degradation rates of methylene blue (MB) were normalized by surface area of TiO₂, showing that the maximum value was found in the anodic oxide with approximately 60% of rutile in the fraction. The specific rate constant for MB degradation was the best in the anodic oxide with low lattice strain and the crystallite size of appropriately 40 nm.