Nanocasting synthesis of BiFeO₃ nanoparticles with enhanced visible-light photocatalytic activity

Abstract

In this work, monodisperse BiFeO3 nanoparticles with a particle diameter of 5.5 nm were synthesized by a nanocasting technique using mesoporous silica SBA-15 as a hard template and pre-fabricated metal carboxylates as metal precursors. To the best of our knowledge, the synthesized particles are the smallest BiFeO3 particles ever prepared by any method. The samples were characterized by X-ray powder diffraction, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The phase purity of the product depends on the type of carboxylic acid used in the synthesis of the metal precursors, the type of solvent in the wet impregnation process, and the calcination procedure. By using tartaric acid in the synthesis of the metal precursors, acidified 2-methoxyethanol in the wet impregnation process and a calcination procedure with intermediate plateaus, monodisperse 5.5 nm BiFeO3 nanoparticles were successfully obtained. Furthermore, the nanoparticles were applied in photodegradation reactions of rhodamine B in aqueous solution under visible-light irradiation. Notably, the cast BiFeO3 nanoparticles demonstrated very high efficiencies and stability under visible-light irradiation, much higher than those of BiFeO3 nanoparticles synthesized by other synthetic methods. The possible mechanism in the photodegradation process has been deeply discussed on the basis of radical trapping experiments.

Hydrothermal Synthesis of Bismuth Ferrite Hollow Spheres with Enhanced Visible-Light Photocatalytic Activity

“…The determined band gap energy of 2.22 eV is considerably smaller, and thus, redshifted when compared to bulk BiFeO . As we discussed in detail previously, a meaningful comparison of band gap values of different BiFeO samples is not always possible as morphology, size, phase purity, as well as oxygen vacancies have a strong impact on the band gap [ 36 , 40 ]. The redshift is often a result of the strained nature of nanosized materials as well as symmetry breaking in high-surface-area materials.…”

“…The photocatalytic activity of the synthesized hollow spheres is much enhanced compared to bulk material and BiFeO materials free of surface defects [ 23 ]. Furthermore, unsupported BiFeO nanoparticles with a large surface area and an average diameter of approximately 5.5 nm were shown to have a degradation efficiency of approximately during the same time period [ 40 ]. In fact, as previously reported that the photocatalytic activity of BiFeO actually decreases with a reduction in particle size as a result of crystal defects and local distortions [ 36 , 40 , 41 ].…”

“…Furthermore, unsupported BiFeO nanoparticles with a large surface area and an average diameter of approximately 5.5 nm were shown to have a degradation efficiency of approximately during the same time period [ 40 ]. In fact, as previously reported that the photocatalytic activity of BiFeO actually decreases with a reduction in particle size as a result of crystal defects and local distortions [ 36 , 40 , 41 ]. The much-superior photocatalytic activity can be explained by the hollow nature of the photocatalyst.…”

Bismuth-based nanostructured photocatalysts for the remediation of antibiotics and organic dyes

“…BiFeO 3 , one of those Bi-based photocatalysts, has been the subject of intensive research in recent years because it is the only naturally occurring magnetoelectric material with ferromagnetic and ferroelectric properties at room temperature [ 39 , 75 , 87 – 89 ]. Bismuth ferrite has a distorted rhombohedral perovskite structure (ABO 3 ), where A is a corner cation, B is a body-centred middle atom, and O is an oxygen atom or anions attached to the crystal faces.…”

Olive Mill Wastewater Remediation: From Conventional Approaches to Photocatalytic Processes by Easily Recoverable Materials

“…In more detail, bismuth ferrite materials (BiFeO 3 ) are characterized by ferroelectricity and ferromagnetic features [167]. They have been explored as nanofibers [168], nanoparticles [169][170][171], nanosheets [172], nanotubes [173], microspheres [174], and nanorods [175], exploiting their magnetic properties and the 2.2 eV bandgap. Li et al [173] compared the photocatalytic behaviour of BiFeO 3 in the form of nanoparticles, nanofibers, and hollow nanotubes, discovering the superior photoactivity of the latter due to the ultra-thin wall thickness and unique material structure.…”