X‐Ray Diffraction Study on the In‐Situ Crystallization Kinetics in Electrospun PVP/TiO 2 Nanofibers

Abstract

Nanostructured TiO2 has received much attention recently owing to their promising physical properties for photocatalytic applications. The process of photocatalysis is closely related to the electronic band gap which is controlled by shape, surface area and particle size. Elongated structures such as nanofibres are of particular importance because they can provide a high specific surface area for photocatalysis. In this paper, the effect of atmosphere and doping on the crystallisation kinetics of electrospun TiO2 nanofibers has been investigated using high-temperature synchrotron radiation diffraction. Electrospun TiO2 nanofibers were synthesized using titanium isopropoxide, poly (vinyl-pyrrolidone) as a polymer binder, and acetic acid and ethanol as a solvent. Diffraction results showed that the as-synthesized TiO2 nanofibres were amorphous initially but when heated in air they crystallized to form anatase and rutile at 600 °C and 700 °C respectively. However, in argon atmosphere, anatase and rutile formed simultaneously at 700 °C. In the presence of vanadium dopant, both anatase and rutile formed in concert at 500 °C. The effects of atmosphere and doping on the crystallisation kinetics and phase stability of TiO2 nanofibres at elevated temperature are discussed.