Enhanced photocatalytic activity of hierarchical titanium dioxide microspheres with combining carbon nanotubes as “e-bridge”

Abstract Enhancing photocatalytic activity of titanium dioxide (TiO 2 ) by efficient charge separation is essential but challenging. Herein, the recombination between photo-generated e–-h + pairs is effectively hindered owing to the “e-bridge” formed between hierarchical TiO 2 microspheres and carbon nanotubes (CNTs). The as-prepared three-dimensional TiO 2 microspheres covered by intercrossing lamellar crystals are abundant in pores and sharp edges, forming an ideal interface with large surface area and numerous active sites for photocatalysis. Combined with CNTs, the TiO 2 microspheres are connected and stabilized. Moreover, the CNTs serve as pathways for electrons, benefiting the effective separation of e–-h + pairs and accounting for the superior photocatalytic activity. Transient fluorescence spectra shows that the lifetime of electrons on TiO 2 prolongs from 5.23 ns to 10.14 ns assisted by CNTs. In aqueous matrix, electrons gathering on the CNTs can react with O 2 to produce O 2 –, and simultaneously, plenty of holes left in TiO 2 host generate OH by oxidizing adsorbed H 2 O, producing abundant active species for photocatalytic degradation of 4-nitrophenol. The highest degradation efficiency in removing organic contaminants is achieved on TiO 2 @CNTs hybridized with CNTs weight ratio being 5%.