Nanostructured TiO_2 Arrays Obtained at Low and High Potential

摘要

Synthesis and characterization of nanostructured TiO_2 arrays obtained by electrochemical anodization of Ti foils at low (＜3V) and high (50V) potential, using different electrolyte solutions, are presented. Scanning electron microscopy studies indicated that at low potential film formation is characterized by a porous array with pore length ＜ 1 micrometer, whereas at high potential it corresponds to a nanotube array with nanotube length of 8 micrometers. The difference in surface roughness between the porous and nanotube arrays did not agree with the photocurrent difference observed in a photoelectrochemical cell, suggesting the presence of limiting phenomena in the longer tubes for this application. Electrochemical impedance studies revealed low capacitance and large pore resistance in TiO_2 nanotubes, which point out to restricted ion diffusion in photoelectrochemical devices working at low bias, as well as different surface reactivity.