Electrospun nanofibers of p-type BiFeO₃/n-type TiO₂hetero-junctions with enhanced visible-light photocatalytic activity

Abstract

One-dimensional BiFeO 3 /TiO 2 heterostructure nanofibers with high visible-light photocatalytic activity have been successfully obtained via a facile hydrothermal process followed by an electrospinning technique. The results show that the BiFeO 3 /TiO 2 nanofibers are as long as dozens of micrometers with the diameters of about 100-300 nm, where BiFeO 3 nanoparticles are surrounded by anatase-type TiO 2 nanocrystals. Compared with the corresponding pure BiFeO 3 nanoparticles, and TiO 2 nanofibers, the asprepared BiFeO 3 /TiO 2 nanofibers exhibit a markedly enhanced photocatalytic activity in the degradation of methyl blue under visible light irradiation. The enhanced photocatalytic activity is attributed to the formed p-n heterojunction between BiFeO 3 and TiO 2 , which results in synergistic enhancement.Notably, the BiFeO 3 /TiO 2 nanofibers could be easily recycled without the decrease in the photocatalytic activity because of their one-dimensional nanostructural property. With their high degradation efficiency and fine recyclability, the BiFeO 3 /TiO 2 heterostructure nanofibers will have wide application in photodegradation of various organic pollutants.

Enhanced visible-light activities of porous BiFeO3 by coupling with nanocrystalline TiO2 and mechanism

“…The VB and CB position of TiO 2 and BFO at point of zero charge on standard hydrogen electrode scale (ca 4.5 eV) can be calculated by E VB = X -E e + 0.5 E g and E CB = E VB -E g , respectively. Thus, the E VB levels for TiO 2 and BFO stand at 3.0 and 2.28 eV, respectively, and their E CB levels are positioned at -0.2 and +0.21 eV [17,37]. Thus, the energy gap (Eg) between the TiO 2 E CB and the BFO E VB is 2.48 eV, corresponding to the light energy of 500 nm by the equation: λ=1240/Eg.…”

“…It is confirmed that the diffraction peaks of TiO 2 are ascribed to the anatase phase (JCPDS Card No. 21-1272) [17].…”

“…They 6 investigated that titania can be made photochemically active under visible light with a wavelength of 460 nm by supporting on BFO substrate. Yang et al [17] have fabricated one dimensional TiO 2 and BFO nanofibres by an electrospinning technique. They investigated that BFO/T nanocomposites exhibit high photocatalytic activity for degrading methylene blue under visible light irradiation, due to the excellent charge separation properties of the heterojunction formed between BFO and TiO 2 .…”

“…In addition, the XPS peaks are slightly shifted toward low binding energy, suggesting that an intimate contact exist between the interface of TiO 2 and P-BFO. [17,26] In general, the band bending at the interface mainly originates from the surface defects. Greater the surface defects at the interface of binary metal oxides, smaller will be the band bending and hence induces smaller conduction band offsets.…”

Photo-induced activity of BiFeO 3 /TiO 2 nanotube arrays derived from ultrasound-assisted successive ionic layer adsorption and reaction

“…BiFeO 3 is a typical perovskite material with rhombohedral structure and one kind of the multiferroic materials which exhibit both ferroelectricity and magnetic ordering at room temperature [8,9]. BiFeO 3 material has been regarded as a promising photocatalyst due to its proper band gap (2.2-2.7 eV), which allows its visible light response [10][11][12]. In general, synthetic methods of BiFeO 3 materials include hydrothermal method, sol-gel, pulsed laser deposition, coprecipitation method, etc [10][11][12][13][14][15].…”