Ensuing the formation of photocatalytic TiO2/Fe2O3 nanocomposite from heat treatment of electrophoretically deposited TiO2 films on stainless steel

Abstract

In this study, thermal transformations in electrophoreticlly coated TiO2 coatings on SS-316L substrate were investigated. Such films were previously employed for antibcaterial purposes, however their heat-treatment at 900 °C resulted in an unexpected transformation in the film color. This study was designed to trace back the origin of such optical transformation in the TiO2 film that was expected to be whitish in its outlook, however it became brownish at elevated temperature, indicating an exploitable characteristics of visible light absorbance. The films were carefully transformed to particles by subsequently applying scratching/ball milling method and characterized through various materials’ characterization tools including but not limited to SEM-(EDS), XRD, alongside characteristic characterizations such as TGA, UV-Vis and EIS for elucidating thermal, optical and electrochemical behavior respectively of particles obtained from pristine (TiO2) and heat-treated films (termed as TFNC) owing to the transformation of TiO2 to TNFC (i.e. TiO2/Fe2O3) nanocomposite. TFNC exhibited decreased band gap from 3.2 eV to 2.86 eV and consequently improved photocatalytic activity. The TFNC degraded 50% Rhodamine B dye under visible light, while pure TiO2 degraded only 13%, which was credited to the formation of Fe2O3 particles inside TiO2 film. It was estimated that the Fe-element was capable to diffuse inside such TiO2 film and resulted the formation of TFNC at ≥ 900°C. The evolution of visible light dependent photocatalytic performance in TFNC was credited to the lowering of bandgap and enhanced electron-hole generation as investigated by EIS.