Hydrothermal modification of TiO2 nanotubes in water and alkali metal electrolytes (LiNO3, NaNO3, KNO3) – Direct evidence for photocatalytic activity enhancement. (10th September 2022)

• Record Type: Journal Article
• Authors: Wtulich, Mariusz; Szkoda, Mariusz; Gajowiec, Grzegorz; Jurak, Kacper; Trykowski, Grzegorz; Lisowska-Oleksiak, Anna
• Is Part Of: Electrochimica acta. Volume 426(2022)
• Publication Date: 2022-09-10
• Subjects: TiO2 nanotubes -- Hydrothermal annealing -- Redshifted VIS absorbance -- Interference; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2022.140802
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: The influence of hydrothermal annealing (HA) of TiO2 nanotubes (TiO2 -NTs) in various baths (H2 O, LiNO3, NaNO3, KNO3 performed for 4 h, 24 h, 64 h), on their photocatalytic and photoelectrocatalytic properties, was studied. The use of electrolytes was to enable the monitoring of photoactivity changes as a result of the expected impact on the population of hydroxyl groups on the surface. The assumption turned out to be correct and it was proved that the presence of Li +, Na + or K + does not allow achieving the same increases in photoactivity as observed for water. Modified samples exhibit significantly decreased F, P and carbon containing species. The length of the HA annealing time considerably affected the geometry of the nanotubes: eliminated clusters, changing the tilting angle of nanotubes, the wall thickness and inter-nanotube distance. Morphology changes due to HA treatment were associated with the interference phenomenon recorded as maximum in the Vis range. HA treatment in water brings about the most photoactive and photoelectroactive material characterized with minor modification in the optical bandgap and position of the flat bad potential. The optical energy bandgap values for electrodes containing alkali metals were reduced (up to 2.72 eV) and flat-band potential was shifted towards the anodic direction (up to 0.25 V disparity). However, increased activity as photocatalysts in the methylene blue degradation process and higher photocurrent generation was achieved for samples after modification in distilled water than in electrolytes, but these parameters are still better in comparison to unmodified titania nanotubes. Long-term treatment in water and electrolytes reduced threshold potentials for oxygen evolution reaction. The studies confirmed the effectiveness of the hydrothermal method for obtaining better photocatalytic parameters of TiO2 -NTs and indicate that the presence of alkali metals is not favourable for maintaining high photocatalytic parameters.