Supplementary material from "Photoelectrochemical performance of BiOI/TiO₂ nanotube arrays (TNAs) p-n heterojunction synthesized by SILAR-ultrasonication-assisted methods"

In order to extend the visible region activity of titania nanotube array (TNAs) films, the Successive Ionic Layer Adsorption and Reaction (SILAR)-ultrasonication-assisted method has been used to prepare BiOI-modified TiO₂ nanotube arrays (BiOI/TNAs). The band gap of BiOI/TNAs for all the variations reveals absorption in the visible absorption. The surface morphology of BiOI/TNAs is shown in the nanoplate, nanoflake and nanosheet forms with a vertical orientation perpendicular to TiO₂. The crystalline structure of BiOI did not change the structure of the anatase TNAs, with the band gap energy of the BiOI/TNAs semiconductor in the visible region. The photocurrent density of the BiOI/TNAs extends to the visible-light range. BiOI/TNAs prepared with 1 mM Bi and 1 mM KI on TNAs 40 V 1 h 50 V 30 min show the optimum photocurrent density. A tandem dye-sensitized solar cell (DSSC)-photoelectrochemical (PEC) was used for hydrogen production in salty water. BiOI/TNAs optimum was used as the photoanode of the PEC cell. The solar to hydrogen conversion efficiency (STH) of tandem DSSC-PEC reaches 1.34% in salty water.