Synthesis of Photocatalytic Active Titanium Dioxide Nanotubes and the Effect of Calcination
Abstract
Photocatalytic active, well-ordered TiO2 nanotubes (TNTs) were synthesized using electrochemical anodization of a Ti substrate. A third generation electrolyte comprising mixture of ethylene glycol and ammonium fluoride in water was used to grow the TNTs at 60 V and 2 h deposition time. The effect of post- annealing on the physical properties and the photocatalytic activity of the TNT samples at two different temperatures, 300C and 400C was investigated. Further, the effect of pre-annealing of Ti substrate foil before growth of TNTs between 250C and 650C was investigated. Calcining at 300C and 400C for 1 h transformed the TNTs from amorphous to anatase phase. SEM images reveal dense and self-organization of TNTS for Ti foils annealed at 350oC and 440oC. The photodegradation rate of MB was twice as high for samples annealed at 400C compared to those annealed at 300C. The length of the TNT reached a maximum of 8.85 m on Ti foils pre-annealed to 440C for 1 h, after which a drastic reduction to 4.87 m and 4.24 m was observed on Ti foils pre-annealed to 525C and 625C respectively. The wall thickness systematically decreased as 32 nm, 31 nm, 29 nm, 21 nm, and 20 nm, respectively, when TNTs were grown on Ti foils heated at 250oC, 350oC, 440oC, 525oC, and 625oC.
Keywords
Anodic, Titanium dioxide, Nanotubes, Photocatalytic