Synthesis and properties of ultra-small BiFeO3 nanoparticles doped with cobalt

Bismuth ferrite (BiFeO3, BFO) is the most promising material in the field of multiferroics. Additionally, it has excellent potential in photocatalysis applications due to its relatively small bandgap, stable structure, and low cost. Doping this material and enhancing its particle size showed promising results in many applications, especially photocatalysis, but the effect of both parameters has never been combined and studied before. In the present work, we report on the effect of cobalt doping of bismuth ferrite Bi Fe1-xCoxO3 x (with x = 0, 0.02, 0.04, 0.06 and 0.08) synthesized by hydrothermal route. The crystalline phase was obtained at a temperature as low as 200 °C. Rietveld's refinement of X-ray diffraction (XRD) confirmed the rhombohedral structure of the crystalline powders. Transmission Electron Microscopy (TEM) alongside High-Resolution Transmission Electron Microscopy (HRTEM) was conducted to probe microstructural features and showed a remarkable decrease in particle size from 12.5 nm to only 4.5 nm, when increasing the cobalt concentration to 8%. The material's optical properties were also studied and showed an increase in band gap values from 2.12 to 2.33eV. The application of the samples to the photodecomposition of methylene blue (MB) under direct sunlight irradiation was reported and have shown unusual results that were explained by the unique sizes of the samples and the phenomena that can occur at that order of magnitude.