TiO2 nanotube arrays treated with (NH4)2TiF6 dilute solution for better supercapacitive performances

- A new hydrothermal approach using dilute (NH4)2TiF6 solutions has been developed.
- The effects of (NH4)2TiF6 treatments have been systematically investigated.
- The morphology of TiO2 nanotubes changed greatly after (NH4)2TiF6 treatment.
- The capacitance of TiO2 nanotubes increases significantly after (NH4)2TiF6 treatment.

Anodic TiO2 nanotube arrays (ATNAs) have been one of the promising electrode materials for supercapacitors due to good chemical stability, large surface area and simple fabrication method. However, the specific capacitance of ATNAs is generally low. Here, we focus on the hydrothermal treatments of ATNAs in (NH4)2TiF6 dilute solutions. After the (NH4)2TiF6 hydrothermal treatments, the smooth wall of ATNAs became rough, a layer of nanoparticles were generated on the surface of nanotubes concurrently. The specific capacitance of the hydrothermally treated ATNAs increased remarkably due to the special nanostructure composed of rough tube walls and the nanoparticles embedded on the tube walls. After the hydrothermal treatment in 0.01 M (NH4)2TiF6 aqueous solution at 120 °C for 45 min, the ATNAs exhibit a specific capacitance of 31.12 mF cm−2, about a 3.1-fold improvement over the untreated ones.

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