Effect of defects on photocatalytic activity of rutile TiO₂ nanorods

To further understand the effect of structural defects on the electrochemical and photocatalytic properties of TiO₂, two synthetic approaches based on hydrothermal synthesis and post-synthetic chemical reduction to achieve oxygen defectimplantation were developed herein. These approaches led to the formation of TiO₂ nanorods with uniformly distributed defects in either the bulk or on the surface, or the combination of both, in the formed TiO₂ nanorods (NRs). Both approaches utilize unique TiN nanoparticles as the reaction precursor. Electron microscopy and Brunauer-Emmett-Teller (BET) analyses indicate that all the studied samples exhibit similar morphology and similar specific surface areas. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) data confirm the existence of oxygen defects (VO). The photocatalytic properties of TiO₂ with different types of implanted VO were evaluated based on photocatalytic H₂ production. By optimizing the concentration of VO among the TiO₂ NRs subjected to different treatments, significantly higher photocatalytic activities than that of the stoichiometric TiO₂ NRs was achieved. The incident photon-to-current efficiency (IPCE) data indicate that the enhanced photocatalytic activity arises mainly from defect-assisted charge separation, which implies that photo-generated electrons or holes can be captured by VO and suppress the charge recombination process. The results show that the defective TiO₂ obtained by combining the two approaches exhibits the greatest photocatalytic activity enhancement among all the samples.