Visible light active Fe doped TiO2 nanowires grown on graphene using supercritical CO2
Visible light driven TiO2 photocatalyst nanowire arrays doped with Fe were grown on the surface of functionalized graphene sheets (FGSs) using a sol–gel method in the green solvent, supercritical carbon dioxide (scCO2). The morphology of the synthesized catalysts was studied by SEM and TEM, which showed uniform formation of Fe doped TiO2 nanowires on the surface of the graphene sheets, which acted as a template for nanowire growth through surface –COOH functionalities. Increasing Fe content in the nanowires gave only small changes in morphology but significantly higher BET surface areas. Optical properties of the synthesized composites were examined by UV and PL spectroscopy which showed a significant reduction in band gap with increasing Fe content, i.e. decreasing from 3.2 to 2.3 eV at 0.6% Fe. High resolution XPS and Raman analysis showed the interaction of Fe with the TiO2 lattice and also bonding of TiO2 with –COOH groups on the surface of the graphene sheets. The photocatalytic properties of the prepared catalysts were evaluated under visible light solar irradiation for the photodegradation of 17β-estradiol (E2), an endocrine disrupting hormone which is commonly released into aquatic environments. All prepared catalysts with different ratios of Fe were active in the visible region of the solar spectrum with the photocatalytic activity significantly enhanced with increasing Fe doping levels with a plateau at 0.6–0.8% Fe. The prepared catalysts showed higher activity than both Fe doped TiO2 and TiO2/FGSs composites.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Graphene sheets used as a catalyst mat to grow Fe doped TiO2 nanofibers from its surface in the green solvent, supercritical carbon dioxide. ► High surface areas and direct attachment were shown by several physico-chemical techniques. ► 17β-Estradiol (E2) was completely degradated by this catalyst in the visible region. ► Fe doped TiO2 on the graphene sheets showed higher photocatalytic activity compared to similar catalyst without graphene.
Journal: Applied Catalysis B: Environmental - Volume 110, 2 November 2011, Pages 25–32