Efficient and rapid sunlight-driven photocatalytic degradation of methylene blue dye using multiferroic BiFeO3 nanoparticles

The current investigation presents a facile and cost-effective sol-gel approach for the synthesis of phase-pure multiferroic bismuth ferrite (BiFeO3) nanoparticles (BFO NPs) by using propylene glycol as a complexing agent, intended for use as a photocatalyst to efficiently degrade organic dyes in aqueous solutions under natural sunlight. Characterization techniques, including thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), elucidated a plausible reaction pathway for the formation of phase-pure BFO NPs. Rietveld refinement of the XRD data, in conjunction with transmission electron microscopy (TEM) and Raman spectroscopy, confirmed the synthesis of single-phase BFO NPs at 400 °C, displaying a space group of R3c and an average crystallite size of 25 nm. UV–visible diffuse reflectance spectroscopy revealed an absorption cut-off wavelength near 590 nm, corresponding to a band gap of 2.08 eV, indicating the capability of BFO NPs to absorb visible light within the 400–590 nm range. BFO NPs have shown efficient and rapid photocatalytic degradation of methylene blue (MB) in acidic, neutral, and basic pH conditions under natural sunlight. This is attributed to the intrinsic ferroelectric and ferromagnetic ordering present in synthesized BFO NPs which facilitates the separation and migration of photoinduced charges through band bending phenomena at the interface.