Electrochemical synthesis, studies and modification of TiO2 nanotubes

Abstract

TiO2 nanotubes (TiO2 NTs) were synthesized using the electrochemical method in a 1 M H2SO4 + 0.15% HF electrolyte. The initial nanotubes have a diameter of 100 ± 10 nm (with the length of up to 150–200 nm) and a wall thickness of 20 ± 5 nm. Nanotube treatment at 400°C results in negligible changes in their structure compared to the initial samples. At 600°C, a change occurs in the nanotube structure and morphology, i.e., the amount decreases drastically; the diameter changes; and, as a consequence, the surface area value decreases. Changes in the structure lead to changes in the electrochemical properties, which is apparently related to a transition from the amorphous structure to anatase and rutile. It is shown that a reversible two-electron reaction, including hydrogen intercalation and Ti4+/Ti3+ oxidation/reduction in the potential range of (−0.6−0.4 V), occurs as a result of moderate thermal treatment. The possibility of the use and promising character of TiO2 NTs as support for a nonplatinum catalyst based on cobalt tetra(p-methoxyphenyl)porphyrin are brought to light. The electrocatalytic activity of the synthesized catalyst per nominal CoTMPP mass in the reaction of O2 reduction at E = 0.7 V is ≈25 A/gCoTMPP, which is comparable to nonplatinum systems on a carbon support.