Oxygen Rich Titania: A Dopant Free, High Temperature Stable, and Visible-Light Active Anatase Photocatalyst

Abstract

High temperature stable and visible light active titania nanomaterials were developed through an aqueous peroxo-titania route. An FT-IR study of the H2O2 modified Ti precursors confirmed the formation of Ti-H2O2 complex. The effect of H2O2 concentration on the high temperature stability of Ti-H2O2 complex was analyzed using Differential scanning calorimetry. High temperature anatase phase stability associated with a decrease in crystallite size and increase of lattice parameters were confirmed using X-Ray diffraction (XRD) and Raman spectroscopy. The high temperature stability and visible light absorption of these materials were found to be proportional to the H2O2 concentration. Presence of stronger Ti-O-Ti bonds and oxygen excess defects in H2O2 modified titania (responsible for high temperature stability and visible light activity) were identified using FT-IR spectroscopy and X-Ray photoelectron spectroscopy (XPS). The H2O2 modified titania samples have superior textural properties in comparison to the control sample. All the H2O2 modified samples were more photoactive and the thermally most stable composition 1:16 H2O2-TiO2 exhibits 5.8 fold visible light activity in comparison to the control sample at 900 °C. It is proposed that the oxygen excess defects in H2O2 modified titania create an energy level above the valence band, which is responsible for efficient visible light absorption.

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