Fabrication of ZnFe2O4/TiO2 nanotube array composite to harness the augmented photocurrent density under visible light

Abstract

ZnFe2O4 micro crystals were deposited over electrochemically anodized TiO2 nanotube array using cathodic electrode deposition method. TiO2 nanotubes owing to their morphological advantage significantly harness the UV region of solar spectrum. However, the optical response of TiO2 nanotube array in visible region is quite negligible due to large band gap. Bare TiO2 nanotubes show a photocurrent density of 0.18 mAcm−2 on exposing TiO2 nanotube electrode to visible light source. However, on mounting ZnFe2O4 over TiO2 nanotubes, the photocurrent density reaches to 0.52 mAcm−2, which is ~ 3 times the photocurrent density shown by bare TiO2 nanotubes under similar conditions. The appreciable enhancement in photocurrent density is attributed to effective visible light active band gap in the resulting hybrid electrode. Moreover, the suitable band edge positions in individual semiconductors facilitate the smooth charge transfer in the resulting hybrid structure on account of band bending at their interface thereby reduces the recombination rate and charge transfer resistance considerably.