Ultrafast microwave-assisted hydrothermal synthesis and photocatalytic behaviour of ferroelectric Fe³⁺-doped BaTiO₃ nanoparticles under simulated sunlight

We report on the synthesis of polycrystalline Fe-doped BaTiO₃ ferroelectric nanopowder that exhibits high visible light photocatalytic activity. The ferroelectric Fe-doped BaTiO₃ samples with nominal Fe contents ranging from 2 to 8 at% are prepared by fast microwave-assisted hydrothermal synthesis. All the doped ferroelectrics exhibit enhanced light harvesting properties due to the charge transfer center of Fe being associated to strong absorption in the visible region. Also, the bulk photovoltaic effect arising from net shift current in the non-centrosymmetric crystal, provides an additional driving force to charge carrier separation. While the best photocatalytic activity is obtained with the 2 at% Fe³⁺-doped BaTiO₃ ferroelectric, the more heavily doped systems show a gradual decrease in photoactivity. In comparison to the undoped BaTiO₃, all the Fe³⁺-doped systems show improved photocatalytic activity under similar experimental conditions. We invoke the iron-associated absorption for an enhanced charge carrier generation and the bulk photovoltaic effect, a property of non-centrosymmetric crystals, for an enhanced charge carrier separation and migration.