Novel anodizing procedure to grow TiO₂ nanotubes successfully employed in ethanol photolysis

Qualitative determination of acetaldehyde produced by oxidation of ethanol in a photoelectrochemical cell is reported as an indicator of the effectiveness of a nanotubular titanium dioxide thin film for hydrogen production by photolysis in separate chambers. The titanium dioxide thin film was grown using a novel anodizing procedure on a 2cm2 titanium foil, varying the anodizing voltage between 80V and 20V during one and five minutes, respectively, for two hours in a 0.10%wt. NH₄F solution in ethylene glycol and using a 4cm2 titanium foil as cathode. The photoelectrochemical cell was formed by two borosilicate glass-chambers separated by a salt bridge of agar-agar and LiCl, UVA lamps, a Ti cathode and the anodized foil as anode, submerged in ethanol 93vol.% and connected by a copper wire in series with a voltmeter. For acetaldehyde determination, two qualitative methods were used: first, the reaction of the ethanol-water solution, after 4 hours of photolysis, with NaOH and heating; the second test was the reaction of a different solution with 2,4-dinitrodiphenyl hydrazine dissolved in methanol. Both assays were positive for aldehyde.