Enhanced photocatalytic performance of titanium dioxides by modulating defect contents and carbon deposits through a simple gas–solid interface reaction

Abstract

The photocatalytic performance of titanium dioxide (TiO₂) is limited by its narrow light absorption range and rapid photogenerated electron–hole recombination. To tackle this issue, reduction treatment of TiO₂ was utilized to bring in defects, for instance, Ti³⁺ ions and oxygen vacancies (VO), enhancing the photocatalytic activity of TiO₂ and extending its light absorption from the ultraviolet to the near-infrared region. In this study, modified TiO₂, featuring Ti³⁺ ions, oxygen vacancies (VO), surface-deposited carbon and stable anatase crystal structures even at high temperatures (>600 °C), was successfully prepared via a simple gas–solid interface reaction between ethanol vapor and anatase TiO₂ powder. The existence of Ti³⁺, VO and a deposited carbon layer (DCL) was characterized using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM). The photocatalytic activity of the modified TiO₂ was assessed via photocatalytic degradation of rhodamine B (RhB), showing a degradation ratio of 96% under solar light and 58% under visible light after 60 minutes of illumination. The degradation mechanism was also discussed.