Synthesis of defect-rich hierarchical sponge-like TiO2 nanoparticles and their improved photocatalytic and photoelectrochemical performance

Defect-rich hierarchical sponge-like TiO₂ nanoparticles were successfully synthesized via the combined one-step hydrothermal method and chemical reduction approach. SEM and TEM images showed their porous structure densely packed with even smaller TiO₂ particles, while photocatalytic results manifested their superior photocatalytic performance and high stability. The RhB solution (10 ppm) could be absolutely degraded in 60 min, and the degradation rate was twice that of the sample without the treatment by NaBH₄. Besides, the TC solution (10 ppm) could be removed by 74.3% in 20 min. PEC measurements also displayed that the photoelectrode based on such defect-rich TiO₂ nanoparticles had small resistance and improved charge transfer rate. The improved performance can be assigned to rich defects and phase junctions, which was supported by characterization results. The presence of rich defects and phase junctions could not only promote the separation of photogenerated charge carriers, but also accelerate the electron transfer, beneficial for both the photocatalytic and the PEC performance. It is expected that the obtained hierarchical sponge-like TiO₂ nanoparticles with rich defects have great potential for photocatalytic applications.