Single-crystalline and reactive facets exposed anatase TiO₂ nanofibers with enhanced photocatalytic properties

Single-crystalline anatase TiO₂ nanofibers with highly reactive {001} facets were synthesized from layered potassium titanate K ₂Ti₂O₅via topotactic transformation in ion-exchange and dehydration. The cuboid fibers showed one-dimensional (1-D) orientation in the [010] direction and {001} as well as {100} facets enclosing along the longitudinal dimension. The structural evolution was deduced from XRD, SEM and TEM characterizations, which revealed that the highly reactive {001} facets were derived from the interlayer splitting and exfoliation of the layered precursors in a surfactant-free way. Photoluminescence (PL) measurements witnessed the efficient separation and transfer of photoinduced charge carriers in the single-crystalline and reactive facets enclosed TiO₂ nanofibers. Sequently, highly efficient photocatalytic property of the nanofibers was demonstrated by phenol degradation and H₂ evolution. Phenol degradation rate of nanofibers is 2.7 times of the irregular-shaped nanoparticle counterparts with the same crystal phase and similar specific surface area. In photocatalytic evolution of H₂, nanofibers presented much higher and more stable activity than both nanoparticle counterparts and P25 benchmark. Charge carrier highways provided by single-crystalline 1-D structures and efficient surface reactivity offered by exposed facets are the two key factors for the enhanced properties.