The morphological transition of anodic TiO2 nanostructures in HF-based mixture electrolytes

초록

It is well-known that anodization of titanium in limited conditions allows the production of highly organized nanotubular TiO2 nanostructures, which can be morphologically transformed to other types of nanostructures such as nanowhiskers, and microcones by controlling anodizing conditions. However, detailed mechanism and electrochemical conditions were not clearly demonstrated yet. Herein, we systematically investigate the morphological transition of self-organized TiO2 nanostructures in terms of anodic potentials and the concentration of mixed electrolytes, showing the maps of the conditions for producing TiO2 nanotubes and microcones. We found that generally, as the voltage goes up and the concentration of HF goes down in the mixture electrolyte, TiO2 nanostructures change from the nanotubes into the microcones. Because of various functional properties of TiO2, we expect that these findings help tailoring the morphology of TiO2 nanostructures, which can be applied for water splitting, dye-sensitized solar cells(DSSCs), photocatalysis, and gas sensors.