Structural features, magnetic properties and photocatalytic activity of bismuth ferrite nanoparticles grafted on graphene nanosheets

Graphene based visible light responsive photocatalysts have been actively used. Among various photocatalysts, bismuth ferrite (BiFeO3), with a suitable band gap, has gained more attention. In this work, BiFeO3 nanoparticles were prepared and grafted on graphene nanosheets (BiFeO3-g-GNS). The morphology, photocatalytic, structural, optical and magnetic properties of BiFeO3-g-GNS were investigated. The XRD analysis shows that the crystalline BiFeO3 nanoparticles have a rhombohedral crystal structure with the R3c space group. Well decorated graphene nanosheets (GNSs) with spherical perovskite type BiFeO3 nanoparticles (50-80 nm) are obtained, as confirmed by FESEM and HRTEM analysis. The Raman spectra and XPS spectra confirm the presence of different valence states (Fe3+, Bi3+) and chemical bonding (Fe-O, Bi-O) in BiFeO3. The M-H curves (at 10, 297 and 380 K) do not show any hysteresis after grafting on the GNSs. Moreover, the magnetic domain structure and the magnetization behavior of the BiFeO3 nanoparticles were discerned by MFM. The presence of GNSs reduces the band gap of BiFeO3 to 2.07 eV (BiFeO3-g-GNS) from 2.15 eV (pristine BiFeO3). Improved photoluminescence (PL) characteristics and a higher BET surface area have also been observed in the case of BiFeO3-g-GNS. The photocatalytic activities of pristine BiFeO3 and BiFeO3-g-GNS were tested by the degradation of cationic methylene blue (MB) and anionic methyl orange (MO) dyes. It has been observed that BiFeO3-g-GNS exhibits a higher photocatalytic activity toward MB (87%) and MO (35.9%) than the pristine BiFeO3 (57.9 and 4.1% respectively). Hence, the rate of photocatalytic degradation of the MB and MO dyes is significantly enhanced in the case of BiFeO3-g-GNS compared to pristine BiFeO3. The higher catalytic activity of BiFeO3-g-GNS is attributed to its lower band gap, higher absorption in the visible region and reduced recombination of photogenerated electron/hole pairs in the presence of GNS. Herein, we demonstrate that the photocatalytic activity of the BiFeO3 nanoparticles can be enhanced by grafting them on GNSs without influencing their magnetic and structural properties.