Oxygen Level Controlled Polymorphic Transformation in Sol–Gel Processed Electrospun TiO₂ Nanofibers

Abstract

The anatase phase of titania (TiO2) is familiar for its enhanced photocatalytic activities and smart window applications. In this study, a crystallographic transformation route to achieve nanofibers of anatase TiO2 nanocrystals has been developed through an environmentally controlled sol–gel and electrospinning methods. Two types of TiO2 nanofibers were synthesized using two different sols prepared under 105 and 315 ppm of the O2 environment within an Ar glovebox using titanium isopropoxide precursor and heat-treated at 500 °C for 5 h. The nanofibers were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and transmission electron microscopy (TEM) methods. Both of XRD and TEM analysis confirmed that the nanofibers processed from low O2 condition are anatase. In contrast, mixtures of anatase and rutile phase nanofibers were obtained whose sol was processed under higher O2 condition. As the nanofibers have a higher surface area-to-volume ratio, they would significantly contribute to enhancing the photocatalytic activities of TiO2.