Experimental and Theoretical Investigations of Low-Dimensional BiFeO3 System for Photocatalytic Applications

Abstract

We report on the fabrication of sub-20 nm BiFeO3 (BFO) nanoparticles using a solid-state approach and preferential leching process. The nanoparticles were subsequently used to deposit, through spray pyrolysis, BFO thin films in a rhombohedral (R3c) crystallographic structure. Then, systematic investigations of the optical and the photocatalytic properties were conducted to determine the effects of the particles size, the microstructure and the increased surface area on their catalytic performances. Especially, improved optical properties were observed, with an optical bandgap energy of 2.20 eV compared to reported 2.7 eV for the bulk system. In addition, high optical absorption was obtained in the UV–visible light region reaching up to 90% at 400 nm. The photoelectrochemical measurements revealed a high photocurrent density under visible light irradiation. Besides, density functional theory calculations were performed on both bulk and thin film BFO structures, revealing an interesting comparison of the electronic, magnetic, ferroelectric and optical properties for bulk and thin film BFO systems. Both theoretical and experimental findings show that the alignment of the band edges of BFO thin film is coherent with good photocatalytic water splitting potential, making them desirable photoanode materials.

Narrow Bandgap Inorganic Ferroelectric Thin Film Materials

“…Representative ones are solar cells, [50] ultraviolet detectors, [22] pyroelectric infrared detectors, actuators, [34] which are one of the frontiers and hotspots of high-tech research at present. [27][28][55][56][57] Narrow bandgap inorganic ferroelectric films are classified into the following three categories according to the microstructure of the material: single crystal films, polycrystalline films, and composite films. In Table 1, we summarize the representative highly oriented single crystal thin film materials, polycrystalline materials, and composite thin film materials in recent years.…”

“…Representative ones are solar cells, [ 50 ] ultraviolet detectors, [ 22 ] pyroelectric infrared detectors, actuators, [ 34 ] which are one of the frontiers and hotspots of high‐tech research at present. [ 27–28,55–57 ]…”

“…Ferroelectric materials are generally considered to be wide bandgap semiconductors with bandgaps between 3.0 and 3.8 eV, [24][25][26][27][28][29] and their low absorption coefficient and photocurrent density limit the photovoltaic applications of ferroelectric materials. [30] As shown in Figure 1, photovoltaic materials with a bandgap of 1.0-1.8 eV can absorb the solar spectrum with maximum efficiency (Figure 1a,b), [31] and hexagonal ferrites (h-RFOs) with a narrow bandgap (1.1-2.0 eV) can absorb light in a very wide range of wavelengths (Figure 1c,d).…”

Effect of Sr and Ti substitutions on optical and photocatalytic properties of Bi1−xSrxFe1−xTixO3 nanomaterials

“…[3][4][5][6][7] In our previous work, we have demonstrated an improved optical and photocatalytic performances in low dimensional BFO thin films, owing to their morphology, crystal structure and high surface area. 8 Nonetheless, the band alignment of pristine BFO thin films entails to be adjusted with water redox potentials to efficiently produce hydrogen. 7 This requires further development and search for appropriate element substitutions to avoid relying on a single compound.…”

The Effect of Bi2O3 and Fe2O3 Impurity Phases in BiFeO3 Perovskite Materials on Some Electrical Properties in the Low-Frequency Field

“…More authors have determined some electrical and dielectric properties for materials such as BiFeO 3 thin films [ 15 , 16 , 17 ], for BiFeO 3 doped with rare earths [ 18 ] and for perovskite ferroelectrics (Ba, Sr)TiO 3 type, in the microwave field [ 19 ]. Moreover, theoretical calculations allowed the determination of the band gap energy both for bulk and thin film BFO structures [ 20 ], the obtained values being 2.7 eV (bulk) and 2.5 eV (thin film), with the authors showing that the conduction band contributes most to these differences. The determination of the electrical conductivity (σ) and dielectric permittivity (ε) of the bismuth ferrite crystalline compounds and experimental studies regarding the low frequency and temperature dependence of σ and ε are few in the literature.…”