Enhancement of NOx photo-oxidation by Fe- and Cu-doped blue TiO2.

: The present work is focused on the removal of NOx with reduced blue TiO2 with Fe (blue Fe-TiO2)- and Cu (blue Cu-TiO2)-doped photocatalyst. TiO2 was reduced via lithium in EDA (blue TiO2). Fe and Cu ions were doped in the reduced TiO2 (blue Fe-TiO2 and blue Cu-TiO2). The material resulted in a core-shell structure of amorphous and anatase phase. XPS suggests the existence of Ti3+ species and oxygen vacancies within the structure of TiO2. Additionally, valence bond (VB)-XPS shows the generation of intermediate levels at the band edge of the doped photocatalyst. Photocurrent, electrochemical impedance spectroscopy and cyclic voltammetry confirmed the enhanced charge-separation process in doped reduced TiO2. The photocatalysts were tested for the photo-oxidation of NOx. Blue Fe-TiO2 reveals the efficiency of 70% for NO elimination and 44.74% for NO2 formation. The improved efficiency of the doped photocatalyst is related to the re-engineered structure with Ti3+ species, oxygen vacancies, and charge traps. Electron spin resonance (ESR) measurement was carried out for blue Fe-TiO2 to confirm the formation of reactive oxygen species (ROS). Furthermore, ion chromatography was used to investigate the mechanism of NOx oxidation. In conclusion, the doped blue TiO2 has a strong tendency to photo-oxidize NOx gasses.