Electrochemical growth of porous titanium dioxide in a glycerol-based electrolyte at different temperatures

Abstract

Anodic TiO2 layers on Ti were prepared via a three-step anodization in glycerol containing NH4F (0.38 wt%) and H2O (1.79 wt%) at the constant anodizing potential of 40V and temperatures ranging from 10 to 40°C. It was confirmed that TiO2 growth is thermally activated and transport of oxygen species across the titanium dioxide layer at the pore bottoms is a rate-limiting step of anodization. The morphological characterizations of received anodic layers were performed for all studied temperatures. The structural features of anodic TiO2 such as pore diameter, cell diameter, porosity, pore density and pore circularity were investigated for various anodizing temperatures. It was found that the oxide thickness, pore diameter, cell diameter and porosity of formed TiO2 layers increase gradually with increasing temperature. The pore density and their arrangement analyses showed that the nanoporous anodic titania layer with the lowest density of pores and best pore arrangement was synthesized at 20°C. In addition, photoelectrochemical properties of formed TiO2 layers were investigated as well.