Enhancement in photoelectrochemical ability via re-engineering the band gap of multi-podal titania nanotubes on functionalizing with copper oxide nano-cubes

Abstract

In this study, multi-podal titania nanotube array (anatase) were fabricated via electrochemical anodization technique on employing third generation electrolyte with suitable and sharp optimization of every anodization parameter. In comparison to conventional titania nanotubes, these nanotubes offer sufficient nanotube wall/electrolyte interface and thereby makes the appreciable reduction in electron hole pair recombination rate by immediate involvement of holes and electrons in oxidation and reduction process, respectively. Furthermore, 85 nm diameter variation in these nanotubes from base diameter 263 nm to top diameter 348 nm makes the incoming light to undergo through graded refractive index which in corresponding increases their light harnessing ability. Although morphological advantage of these nanotubes is being efficiently harnessed in the scattering of incident light but the large band gap 3.2 eV still confines their utility to UV region only. To increase their photo-electrochemical potential under visible light as well, these nanotubes were functionalized suitably with Cu2O nano-cubes without disturbing the nanotube morphology. Under the analysis of their photo-electrochemical potential, the photocurrent density recorded for bare and Cu2O functionalized multi-podal titania nanotube array under visible light source 300 W Xenon lamp (1 sun illumination) was 0.27 mAcm−2 and 0.39 mAcm−2, respectively. The enhancement of ~45% in photocurrent density under visible light illumination is attributed to suitable band edge positions in Cu2O with respect to the band edge positions in TiO2 which in corresponding leads the formation of effective visible light active band gap in the resulting hybrid structure.