Effect of Ce conversion underlayer coating on the photo-catalytic activity of TiO₂ sol–gel film deposited on hot-dip GI

By Park, Ji Hoon; Kim, Woo Sung; Jo, Du-Hwan; Kim, Jong Sang & Park, Jong Myung
Published in Journal of Industrial and Engineering Chemistry NULL 2014

Abstract

In the present work, a photocatalytic titanium dioxide (TiO₂) thin film was prepared by dip coating using an alkoxide sol–gel solution that included crystalline nano-sized TiO₂ particles (P-25) on hot-dip galvanized steel (GI). A cerium (Ce) conversion coating was used as an interface layer between the steel substrate and TiO₂ film to improve the photocatalytic activity and anti-corrosion performance of the film. The Ce conversion coatings were deposited on the GI via the sol–gel dip coating process using a Ce nitrate/hydrogen peroxide solution. The properties of the coating layers were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), UV–vis light absorption spectroscopy, and electrochemical impedance spectroscopy (EIS). The thickness of the TiO₂ sol–gel film and Ce conversion coating were approximately 150 nm and 30 nm, respectively. It was clearly demonstrated that the addition of nano-sized TiO₂ particles in the sol–gel film significantly enhanced the film's photocatalytic activity. The higher quantity of nano-sized TiO₂ particles induced a higher absorption of UV light and improved photocatalytic activity. In particular, the photocatalytic activity was improved further by applying the Ce conversion coating because in most cases, the crystalline CeO₂ interlayer reduced the band gap energy of the coating layer from 3.2 eV to 2.8 eV. In addition, the EIS measurements indicated that the Ce conversion coatings improved the anti-corrosion property of the coating layer on the hot-dip galvanized steel.

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