Porosity-dependent photoelectrochemical activity of double-layered TiO₂ thin films deposited by spin-coating method

Photoelectrochemical (PEC) cells made of low-cost, chemically stable, and abundant materials are crucial for green hydrogen production. In this regard, the fabrication of porous films with high light trapping ability and a large contact area is crucial for the production of efficient PEC cells. In this report, anatase TiO₂ thin films with a porous double-layered structure were successfully prepared using a conventional spin-coating deposition method. Various amounts of polystyrene spheres were used as a pore-templating agent to control the porosity of the films. A range of characterization techniques, such as scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and photoluminescence were employed to assess the morphology, structural and optical properties of prepared TiO₂ films. PEC measurements revealed that prepared double-layered TiO₂ thin films exhibit porosity-dependent photocatalytic activity. For example, TiO₂ films with an optimized porous structure demonstrated an increase in photocurrent density by a factor of ∼2.23 (to 141.7 μA cm^-2) and photoconversion efficiency improvement by a factor of ∼2.14 as compared to non-porous double-layered TiO₂ reference films. Absorbance and photoluminescence analysis confirmed that improved PEC activity can be attributed to increased light absorption by the porous structure and reduced charge carrier recombination.