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 H-2 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.