New insights of photocatalytic and magnetic activity of Co‑doped BiFeO3 nanoparticles via competition structures

Abstract Cobalt was chosen as the doping element for BiFeO3 (BFO), and the pure BFO and series of BiFe1-xCoxO3 (x = 0.03, 0.05, 0.07, 0.09) nanoparticles, correspondingly labeled as nBFCO (n = 3, 5, 7, 9), were successfully prepared and investigated based on the sol-gel method in this paper. The synthesized nanoparticles were characterized by X-ray diffraction, field emission scanning electron microscopy, Brunauer−Emmett−Teller surface area, X-ray photoelectron spectroscopy, and ultraviolet-visible light absorption. With the increase of the doping level of cobalt in BFO, a competing structure wandering between rhombohedral and orthorhombic structures were observed in the experiment. For instance, the microstructure characterization clearly indicated that 7BFCO had a coexistence of the rhombohedral and orthorhombic structures. Meanwhile, the bandgap of BFO was significantly reduced from 2.04 eV to 1.78 eV. The photocatalytic degradation of Rhodamine B of samples in an aqueous solution was investigated under different wavelengths of light. We found that 7BFCO was the optimal proportion for acquiring the photocatalytic and magnetic activity in this work, e.g., the photocatalytic efficiency can reach 98.2%, and the underlying physics based on lattice structure, size effect and energy gap is discussed.