Inter-relationship between extent of anatase crystalline phase and photocatalytic activity of TiO2 nanotubes prepared by anodization and annealing method

Abstract

Present work is an investigation of the inter-relationship between the degree of anatase crystalline phase and the photocatalytic activity of TiO2 nanotubes. TiO2 nanotube arrays on Ti foil were fabricated by electrochemical anodization followed by annealing at 480°C for different time lengths (1–9h). Anatase crystalline phase formation is confirmed from Raman spectra. They also reveal an enhancement in crystallinity with increase in annealing time. Photoluminescence spectra also exhibit good crystallinity with fewer surface defects in annealed samples. Morphological study with HRSEM also confirms the same. When subjected to photocatalytic functionality in methyl orange (MeO) dye degradation, both the efficiency and pseudo first order rate constant (k) of MeO increase with increase in annealing time of TiO2 nanotubes. Maximum efficiency of 97.29% and k value of 0.0145min−1 are observed for 9h annealed TiO2 sample. Thus, an improvement in crystallinity of anatase phase facilitates charge separation by reducing surface defects and results in efficient electron transport and ultimately contributes to a greater photocatalytic activity in TiO2 nanotubes.