Enhanced Photocatalytic Activity of Nb-TiO2 Nanotubes

Nb-TiO2 nanotubes were prepared by a solgel-derived electrospinning method at calcination temperatures ranging from 500 to 650 C to determine the effects of the calcination temperature on the crystal structure and photocatalytic activity towards methylene blue (MB) degradation. X-ray diffraction indicated that Nb-TiO2 nanotubes were composed of anatase and rutile phases. The crystal structure was maintained regardless of the calcination temperature. The Brunauer-Emmett-Teller surface area increased slightly from 73.3 m(2)/g to 76.0 m(2)/g with increasing calcination temperature from 500 C to 550 C, but decreased dramatically to 48.5 m(2)/g at 650 C. MB degradation proceeded via pseudo-first order kinetics; the rate constant decreased from 1.93 x 10(-2) min(-1) to 1.23 x 10(-2) min(-1) with increasing temperature from 500 C to 650 C. The Nb-TiO2 nanotubes calcined at 500 C exhibited the highest level of MB degradation (91%) than that of Nb-TiO2 nanofibers (60%). The experimental results indicated that the best photocatalytic activity was achieved using the Nb-TiO2 nanotubes calcined at 500 C.