Facile fabrication of anatase TiO2 nanotube arrays having high photocatalytic and photovoltaic performances by anodization of titanium in mixed viscous solvents

Highly ordered, vertically aligned, one side-opened, and regularly porous anatase TiO2 nanotube arrays (TNAs) have been facilely grown by anodizing Ti foil in mixed viscous solvents of ethylene glycol (EG) and glycerol. By changing the volume ratio of two solvents, we have controlled the structural properties of TNAs such as tube diameters, wall thicknesses, and tube lengths. Our prepared TNAs have been found to have enhanced (004) planes, which are reactive in catalysis reactions. We have demonstrated that TNAs grown in 2:1 (v/v) EG and glycerol have the lowest band-gap energy and the largest mean crystallite diameter. TNAs grown on Ti foil have been directly employed for photocatalytic materials and the working electrode of photovoltaic dye-sensitized solar cells. Among our prepared samples, TNAs grown in 2:1 (v/v) EG and glycerol have shown the best photocatalytic activity for the degradation of methylene blue and the highest photovoltaic conversion efficiency of 4.08 %.