Phase transition and visible light driven enhanced photocatalytic activity of Eu-Ni co-doped bismuth ferrite nanoparticles*

Bismuth Ferrite (BiFeO₃), as a room-temperature multiferroic material has garnered quite attention of the physicists. The low-band gap and high visible-light absorption of BiFeO₃ can be exploited for photocatalytic applications for the degradation of industrial pollutants. With partial substitution of ‘Eu’ and ‘Ni’ at the ‘Bi’ and ‘Fe’ site of BiFeO₃ respectively, there happens to be a structural distortion from rhombohedral (R3c) to a mixed phase comprising of orthorhombic (Pnma) and rhombohedral (R3c) phase, confirmed from Rietveld and Raman analysis.  We observe that Eu-Ni doped BiFeO₃ nanoparticles degrade 2-nitrophenol (50 mg/L) to 99.26 % within 2 hours of irradiation as compared to 69 % for pure BiFeO₃. The creation of deep impurity states below the conduction band owing to the replacement of Fe³⁺ with Ni²⁺, decreases the band gap from 2.17 eV to 2.12 eV and also act as trap centres for charge carriers, thus preventing recombination and enhances the photocatalytic activity. Adsorption of pollutants on the surface of photocatalyst is more for co-doped nanoparticles, owing to its higher porosity as well as increased surface area, hence enhancing photocatalytic activity.