Fabrication of robust TiO₂ thin films by atomized spray pyrolysis deposition for photoelectrochemical water oxidation

Photoelectrodes are highly essential for the photoelectrochemical water splitting process and development of novel fabrication techniques is vital for further enhancement of activity. In this study, we successfully fabricated highly active TiO₂ thin films by using novel atomized spray pyrolysis deposition (ASPD) technique. The ASPD technique utilizes a unique atomization process to produce highly fine aerosols which resulted in a highly crystalline TiO₂ nanostructure. The deposition process was optimized by controlling deposition temperatures and precursor amounts. XRD and SEM studies confirmed the formation of anatase TiO₂ phase and a highly interconnected nano-flakes on FTO substrate at 550 °C. The photoelectrochemical activity of the optimized thin films showed a photocurrent density of ∼5 mA cm⁻² at 1.0 V (vs. Ag/AgCl) in 0.1 M Na₂SO₄ (aq) under 375 nm (150 mW cm⁻²) illumination. This photocurrent was much higher than the two other anatases TiO₂ thin films fabricated by conventional spray pyrolysis deposition (SPD) using the same precursor and anatase TiO₂ powder (particle size ∼21 nm). Transient IR absorption study revealed that the SPD powder based thin films have deeply trapped electrons, whereas ASPD thin films consisted with only free and/or shallowly trapped electrons. Higher crystallinity and enhanced electron conductivity of the TiO₂ thin films fabricated by ASPD are responsible for this stable and high photoelectrochemical activity.