Band gap engineered TiO2 nanoparticles for visible light induced photoelectrochemical and photocatalytic studies

Abstract

Visible light-active TiO₂ (m-TiO₂) nanoparticles were obtained by an electron beam treatment of commercial TiO₂ (p-TiO₂) nanoparticles. The m-TiO₂ nanoparticles exhibited a distinct red-shift in the UV-visible absorption spectrum and a much narrower band gap (2.85 eV) due to defects as confirmed by diffuse reflectance spectroscopy (DRS), photoluminescence (PL), X-ray diffraction, Raman spectroscopy, electron paramagnetic resonance, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and linear scan voltammetry (LSV). The XPS revealed changes in the surface states, composition, Ti⁴⁺ to Ti³⁺ ratio, and oxygen deficiencies in the m-TiO₂. The valence band XPS, DRS and PL results were carefully examined to understand the band gap reduction of m-TiO₂. The visible light-responsive enhanced photocatalytic activity of m-TiO₂ was demonstrated by degrading methylene blue and brilliant blue G. The EIS and LSV in the dark and under visible light irradiation further support the visible light-induced photocatalytic activities of the m-TiO₂ due to a decrease in electron transfer resistance and an increase in photocurrent. This study confirms that m-TiO₂ can be used effectively as a photocatalyst and photoelectrode material owing to its enhanced visible light-induced photocatalytic activity.