Quantitative Comparison of the Photocatalytic Efficiency of TiO2 Nanotube Film and TiO2 Powder

Abstract

We compared the plausible reaction mechanism and quantitative efficiency of highly self-organized TiO2 nanotube (ntTiO2) film with TiO2 powder. Film was fabricated by electrochemical potentiostatic anodization of titanium thin film in an ethylene-glycol electrolyte solution containing 0.3 wt% NH4F and 2 vol% deionized water. Nanotubes with a pore size of 80-100 nm were formed by anodization at 60 V for 3 h. Humic acid (HA) was degraded through photocatalytic degradation using the ntTiO2 film. Pseudo first-order rate constants for 0.3 g of ntTiO2, 0.3 g TiO2 powder, and 1 g TiO2 powder were 0.081 min−1, 0.003 min−1, and 0.044 min−1, respectively. HA adsorption on the ntTiO2 film was minimal while adsorption on the TiO2 powder was about 20% based on thermogravimetric analysis. Approximately five-fold more normalized OH radicals were generated by the ntTiO2 film than the TiO2 powder. These quantitative findings explain why ntTiO2 film showed superior photocatalytic performance to TiO2 powder.