A strategy to fabricate bismuth ferrite (BiFeO3) nanotubes from electrospun nanofibers and their solar light-driven photocatalytic properties

Abstract

A strategy has been developed to produce bismuth ferrite (BiFeO₃/BFO) nanotubes from electrospun nanofibers. It involves ramping the temperature to heat the as-spun BFO/PVP composite fibers to their annealing temperature using different modes, which eventually decides the final morphology of the BFO. Accordingly, we found that using step-by-step and direct ramping modes to reach the annealing temperature, yielded nanofibers and nanotubes of BFO, respectively. From the respective XRD patterns, the average crystallite sizes embedded in the BFO nanofibers and nanotubes were found to be around 15 and 20 nm, respectively. Further, these results were also substantiated through high-resolution transmission electron microscopy images. The field emission scanning electron microscopy images showed that the average diameter of the nanotubes and nanofibers was around 100 nm, while the length varied from one to a few micrometers and the inner diameter of the nanotubes was found to be around 10 nm. The optical characterization of these BFO nanotubes and nanofibers by UV-visible absorption and diffuse reflectance spectrometry showed a band gap energy of around 2.38 eV and a broad UV-visible absorption band between 300 and 500 nm, compared to the BFO bulk particles which showed absorption only in the UV region. This observation promised visible light driven optical activity of these 1D BFO nanostructures. As a result, improved photocatalytic activities were observed in both the BFO nanotubes and nanofibers owing to their quantum efficiency. However, the nanotubes showed a relatively enhanced photocatalytic activity compared to the BFO bulk particles and nanofibers. This could be attributed to the fact that the nanotubes might possess more of the catalytic species on the inner and outer surfaces that degrade the dye molecules. The observed results show that these one-dimensional BFO nanostructures can become super-efficient solar light-driven photocatalysts for environmentally benign applications.