Heterogeneous Photocatalysis with Niobium Doped-Titanium Substrates Treated by Plasma Electrolytic Oxidation

Plasma Electrolytic Oxidation (PEO) was employed for the generation of porous niobium-containing surfaces with enhanced photocatalytic activity. Pulses of 500 and 600 V, with a repetition rate of 60 Hz, were applied to titanium disks immersed in niobium-containing electrolytic solutions. The treatment time ranged from 180 to 600 s, and the surface morphology was analyzed by scanning electron microscopy, while X-ray diffraction was employed in the evaluation of crystallographic structure. The optical gap of the samples was determined from UV-Vis reflection spectra, and an automated goniometer was used for contact angle and surface energy measurements. More than 35% of Nb has been incorporated into the samples. Under certain conditions, the treatments resulted in a reduction of the optical gap from 3.18 to 2.63 eV as compared to as-received samples. Photocatalytic degradation rates of methylene blue as high as 70% have been reached after 120 minutes under irradiation with UV-Vis light.

Keywords:
Photocatalytic activity; titanium; niobium oxide; plasma electrolytic oxidation; PEO