A facile route to accelerate the formation of TiO2 nanotube arrays

Highly ordered TiO2 nanotube arrays fabricated by electrochemical anodization of titanium have attracted significant attention due to their splendid promising applications. One of the factors limiting the application of TiO2 nanotube arrays was their long sustaining reaction time by anodic oxidation, usually lasting 6 – 12 h and even longer when systhesizing thicker nanotubular layers. In this paper, we reported for the first time a facile and effective route to accelerate the formation of TiO2 nanotube arrays by proper proportional addition of sodium carbonate(Na2CO3) into the anodization electrolyte. In our experiments, we adopted the 0.3 wt% NH4F + EG (ethylene glycol) + 3.0 vol% H2O electrolyte and we added Na2CO3 with the proportion n(NH4F) : n(Na2CO3) = 1:1, 2:1, 3:1, 4:1 and 5:1. The field-emission scanning electron microscope (FESEM) characterization results suggested the Na2CO3 additives accelerated the growth rate of the TiO2 nanotubes with the quickest growth rate 1100 nm/min when n(NH4F) : n(Na2CO3) = 2:1. Finally, we investigated the mechanism of the Na2CO3 additives accelerating the growth rate of the TiO2 nanotubes. It was believed that the hydrolyzation of the Na2CO3 additives in the electrolytes accelerated the formation of the TiO2 nanotubes and at the same time restrained the chemical dissolution of the formed TiO2 nanotubes.