Preparation and photoelectrochemical properties of a hybrid electrode composed of polypyrrole encapsulated in highly ordered titanium dioxide nanotube array

We demonstrated in this paper that polypyrrole encapsulated in highly ordered TiO₂ nanotubes array (PPy/TiO₂ NTs) electrode could be obtained via two steps: (1) electrosynthesis of TiO₂ nanotube array in HF solution by anodization method; (2) followed by electropolymerization of pyrrole encapsulated in the TiO₂ nanotubes array. The morphological characteristics and structures of PPy/TiO₂ NTs electrode were examined by field-emission scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy. The photoelectrochemical properties were studied in a three-electrode cell with 0.5 M Na₂SO₄ solution as supporting electrolyte. The photocurrent was dramatically enhanced on the PPy/TiO₂ NTs electrode, comparing with that on bare TiO₂ NTs electrode. A photocurrent density of 1.52 mA cm^{- 2} and the incident photon to electron conversion efficiency of 73.21% were obtained under an UV illumination of 10 mW cm^{- 2}.