Fabrication of a coral/double-wall TiO2 nanotube array film electrode with higher photoelectrocatalytic activity under sunlight

Abstract

A coral/double-wall TiO₂ nanotube array (coral/DWNT TiO₂) film electrode was synthesized via anodic oxidation in an ultrasonic bath in an organic electrolyte containing 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]). The morphology, crystal structure, chemical state, and optical properties of the TiO₂ film were characterized via field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and UV-Vis absorption spectroscopy. The results showed that the film had a unique lower layer DWNT/upper layer coral structure with a mixed phase of anatase and rutile. The XPS results proved that the interstitial nitrogen atoms doped in the TiO₂ crystal lattice as a Ti–O–N bond. The coral/DWNT TiO₂ film exhibited evident absorption in the range of 400 nm to 800 nm and significant photoelectrocatalytic activity under sunlight.