Mesoporous TiO2 photocatalytic films on stainless steel for water decontamination

Abstract

Coating of mesoporous TiO₂ nanocrystalline films on stainless steel (Grade 304) was conducted using an evaporation-induced self-assembly (EISA) process in the presence of a PluronicF127 triblock copolymer. The photocatalytic properties of mesoporous TiO₂ films were evaluated using orange II in aqueous solution under ultraviolet irradiation. Surface analysis shows that leaching of metals (e.g., Fe, Cr) from the stainless steel occurred during the EISA process. The leached metal species came to the interface between the titanium species and the copolymer, adversely influencing the self-assembly of the mesophase, leading to a poor mesoporous structure and a low photocatalytic activity in the resultant TiO₂ films. Pre-treatment of stainless steel by acid washing followed by coating a SiO₂–SnO₂ interlayer has been demonstrated to effectively avoid the acid leaching and thermal diffusion of metal species from stainless steel. The photocatalytic activities of the subsequently deposited mesoporous TiO₂ films were significantly improved, which can be attributed to the enhanced charge carrier separation and excellent optical reflection properties of the interlayer.