Influences of air calcination and steam activation on microstructure and photocatalytic activity of continuous TiO2 fibers

Effects of air calcination and steam activation, on phase transformation, microstructure and photocatalytic activity of continuous TiO2 fibers prepared by sol–gel method were studied. The fibers were characterized by XRD, SEM, and N2 adsorption–desorption. The photocatalytic activity was evaluated by photocatalytic degradation of formaldehyde. Results showed that 100% rutile fibers heat-treated in air and steam were obtained at 800 °C and 600 °C, respectively. The anatase grain sizes and special surface areas of the fibers heat-treated at 500 °C in air and steam were 31.6 nm, 22.7 nm, 26.7 m2/g and 32.3 m2/g, respectively. The degradation rates of formaldehyde over the fibers heat-treated at 500 °C in air and steam were 92.3% and 98.6% after 14 h under UV irradiation, respectively. Compared with the air calcination, the steam activation promoted the anatase–rutile phase transformation, reduced the grain size, increased the special surface area, and improved photocatalytic activity of continuous TiO2 fibers.