Study of Structural, Optical, Morphology and Photoelectrochemical Properties of Melanin Sensitized TiO2 Thin Films Prepared by Chemical Bath Deposition Method
Abstract
TiO2 thin films were synthesized using simple, inexpensive, low-temperature chemical bath deposition (CBD) method and annealing at 300, 400, and 500 °C. The obtained TiO2 thin films were sensitized with melanin. Influence of annealing temperature on structural, optical, morphology, and photoelectrochemical cell properties were investigated using a variety of techniques such as low angle X-Ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV-Visible spectroscopy, linear sweep voltammetry (LSV), Mott-Schottky (MS), electrochemical impedance spectroscopy (EIS), etc. We found that sensitization of TiO2 with melanin changed its phase from pure rutile to rutile-anatase mixed-phase and the average crystallite size of melanin sensitized TiO2 films is lower than TiO2 films over the entire range of annealing temperature studied. SEM analysis showed the development of microcracks when TiO2 was sensitized with melanin. UV-visible spectroscopy analysis showed that TiO2 films absorbed mainly in the UV region whereas melanin sensitized TiO2 thin films absorbed significantly in the visible region. Upon melanin sensitization, TiO2 films showed a decrease in current density and flat band potential besides an increase in depletion width when annealing temperature was increased from 300 to 500 °C. Furthermore, EIS analysis revealed that melanin sensitized TiO2 had a high charge transfer resistance. The obtained results showed that the sensitization of TiO2 with melanin was not advantageous for the photocatalytic water splitting.
