(I2)n-encapsulated and C-encapsulated TiO2 films: Enhanced photoelectrochemical and visible-light photoelectrocatalytic properties

Visible-light absorbing (I2)n-encapsulated TiO2 film (I2-TiO2 film) and C-encapsulated TiO2 film (C-TiO2 film) were fabricated and studied as film electrodes for their photoelectrochemical and photoelectrocatalytic (PEC) properties. The as-prepared film electrodes were characterized by scanning electronic microscopy, energy-dispersive X-ray spectroscopy and UV–visible diffuse reflectance spectroscopy. The photoelectrochemical properties were evaluated by the incident photo-to-current conversion efficiency, electrochemical impedance spectroscopy and Mott–Schottky analysis data. The results showed that I2-TiO2 and C-TiO2 films exhibited stronger absorption in the 400–550 nm range, lower electron transfer resistance and more negative flat band potentials comparing with pure TiO2 film. Moreover, the photoelectrochemical ability of I2-TiO2 film is superior to that of C-TiO2 film. At a bias potential of 0.5 vs (Ag/AgCl)/V, the visible-light-induced PEC degradation ratios of rhodamine B and tetracycline on I2-TiO2 film or C-TiO2 film electrodes exceeded that on pure TiO2 electrode, with the improvement by a factor of about 5 or 3. The higher PEC activity of I2-TiO2 film and C-TiO2 film could be attributed to the enhancement of separation of electron-hole pair at the external electric field and the extension of the light response range of TiO2 to the visible light with a red shift in the band gap transition.

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► (I2)n-encapsulated TiO2 (I2-TiO2) and C-encapsulated TiO2 (C-TiO2) film electrodes were prepared.
► I2-TiO2 and C-TiO2 films show improved light absorbance in 400–550 nm.
► Lower electron transfer resistance and more negative flat band potentials were obtained from them.
► The photoelectrocatalytic activities of I2-TiO2 and C-TiO2 films were much higher than TiO2 film.