Selective Removal of the Outer Shells of Anodic TiO₂ Nanotubes

Abstract

A facile electrochemical method to selectively remove the outer walls of anodic TiO2 nanotubes by leaving the as‐anodized nanotubes in the same electrolyte and applying an electric field parallel to the anodic film for several minutes is reported. The better‐separated single‐walled TiO2 nanotubes thus obtained show significantly improved photocatalytic efficiency compared with their non‐etched counterparts.

Quantitative relationship between nanotube length and anodizing current during constant current anodization

“…Despite many elegant investigations and much deeper interpretation on the nanopores or nanotubes have been reported in many famous journals [4][5][6][7][8][9][10][11], until now, the driving force for the pore formation still remains unclear [4,5,12], because it is hardly derived by direct in-situ methods [11]. The generally accepted mechanism for the pore formation in anodic titania films is the field-assisted dissolution (or preferential oxide dissolution) process (equation (1)) [9,[12][13][14], which is similar to that in PAA films (equation (2)) [15][16][17], despite the lack of direct experimental evidence that confirms this expectation [16]. However, this important fact has been ignored for decades, and the reaction (1) has been cited extensively to explain the growth mechanism of ATNTs.…”

Growth of anodic TiO2 nanotubes in mixed electrolytes and novel method to extend nanotube diameter

“…In order to functionalize the TiO 2 , several methods (e.g., sol-gel method, hydrothermal process, vapor deposition, anodization) have been exploited to modify the microstructure and functions of TiO 2 [4,5]. Over the past decade, anodic TiO 2 nanotubes (ATNTs) or porous anodic titania films formed by electrochemical anodization of Ti (or its alloy) have received considerable attention due to their unique self-ordered nanostructures [5][6][7][8]. Meanwhile, the controversial formation mechanism [5,9] and diverse functionalities [12][13][14] are also always research hotspot.…”

Formation Mechanism of Gaps and Ribs Around Anodic TiO2Nanotubes and Method to Avoid Formation of Ribs

“…16 Previous studies have shown that fluorine ions played a significant role in the initiation and growth of TiO 2 nanotubes. [8][9][10] However, ATNTs have been achieved in an aqueous H 2 SO 4 solution as well as other fluoride free solutions. [19][20][21] This fact puts the fluoride effect ([TiF 6 ] 2− ) and the field-assisted dissolution into question.…”