ALD coating of centrifugally spun polymeric fibers and postannealing: case study for nanotubular TiO 2 photocatalyst.

This work describes the synthesis of highly photocatalytically active TiO 2 tubes (TiTBs) by combining centrifugal spinning and atomic layer deposition (ALD). Poly(vinyl pyrrolidone) (PVP) fibers were first produced by centrifugal spinning and subsequently coated with TiO 2 with various film thicknesses in a fluidized bed ALD reactor. After annealing of the TiO 2 ALD coated PVP fibers, TiO 2 tubes (TiTBs) with excellent textural properties and diameters in the range from approx. 170 to 430 nm were obtained. The morphology and structure of all TiTBs were investigated by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller analysis (BET). Liquid phase photocatalysis was conducted to determine the photocatalytic activity of the TiTBs. The photocatalytic activity of the TiTBs obtained after 50 TiO 2 ALD cycles (degradation rate 0.123 min -1 ) was twice that of the reference TiO 2 P25. The underlying reasons for the remarkable photocatalytic performance were textural properties of the resulting tubes along with suitable crystallinity, embedded within the 1D tubular morphology. The herein presented proof-of-concept approach paves a way for the processing of various polymeric fibers into various tubular nanostructures.