Fe doped TiO₂–graphene nanostructures: synthesis, DFT modeling and photocatalysis

In this work, Fe-doped TiO₂ nanoparticles ranging from a 0.2 to 1 weight % were grown from the surface of graphene sheet templates containing –COOH functionalities using sol–gel chemistry in a green solvent, a mixture of water/ethanol. The assemblies were characterized by a variety of analytical techniques, with the coordination mechanism examined theoretically using the density functional theory (DFT). Scanning electron microscopy and transmission electron microscopy images showed excellent decoration of the Fe-doped TiO₂ nanoparticles on the surface of the graphene sheets >5 nm in diameter. The surface area and optical properties of the Fe-doped photocatalysts were measured by BET, UV and PL spectrometry and compared to non-graphene and pure TiO₂ analogs, showing a plateau at 0.6% Fe. Interactions between graphene and Fe-doped anatase TiO₂ were also studied theoretically using the Vienna ab initio Simulation Package based on DFT. Our first-principles theoretical investigations validated the experimental findings, showing the strength in the physical and chemical adsorption between the graphene and Fe-doped TiO₂. The resulting assemblies were tested for photodegradation under visible light using 17β-estradiol (E2) as a model compound, with all investigated catalysts showing significant enhancements in photocatalytic activity in the degradation of E2. (paper)