Tuning the Photoelectrochemical Properties of Narrow Band Gap Nanoporous Anodic SnOx Films by Simple Soaking in Water.

Nanoporous tin oxide layers obtained via anodic oxidation of metallic tin at the potential of 4 V in the alkaline electrolyte (1 M NaOH) were soaked in distilled water for various durations (from 2 h to 120 h) to verify the influence of water-enabled crystallization on the morphology, composition, and related optical and photoelectrochemical properties of such kind of anodic SnOx. Although water soaking generally contributes to more stoichiometric and crystalline tin oxide, it was confirmed that at the initial stages of the water-induced dissolution-redeposition process, material exhibits enhanced photoelectrochemical performance under simulated sunlight irradiation. However, long-time exposure to water results in a gradual widening of the material's band gap, shifting of the photoelectrochemical spectra towards higher energies, and almost complete deterioration of the photoelectrochemical activity under sunlight irradiation.