Ferroelectric Fe–Cr Codoped BaTiO₃ Nanoparticles for the Photocatalytic Oxidation of Azo Dyes

Ferroelectric Fe3+Cr3+ codoped BaTiO3 nanopowders have been successfully synthesized by a microwave-assisted hydrothermal method. The results indicate that by molar adjustment of the cations the apparent optical absorption edge of the codoped ferroelectrics can be red-shifted in comparison to undoped BaTiO3 ferroelectric. The interfacial charge transfer properties of the materials as evaluated through electrochemical impedance spectroscopy (EIS) and chronoamperometry reveal an average charge transfer resistance. The nanopowders are then explored as photocatalysts for the degradation of methyl orange under calibrated solar irradiation. The results show that Fe3+ doping increases the photoabsorption and improves the degradation process for up to 4 mol % in the precursors. For higher concentrations, the effect is reduced due to a partial loss of tetragonality of the ferroelectric material. The best photocatalytic performance achieved with the 4 mol % Fe3+ is 3.7 times higher than that of undoped BaTiO3 nanopowder under otherwise identical conditions. The improvement is ascribed to synergy between ferroelectric polarization and enhanced visible light utilization.