Enhanced photocatalytic activity of TiO2 nanotubes decorated with Ag nanoparticles by simultaneous electrochemical deposition and reduction processes

The photocatalytic activity of the modified TiO2 nanotubes (TNTs) for water purification was studied. Three modification methods including Ag nanoparticles (NPs) decoration (TNT-Ag), electrochemical reduction of the TNTs (TNT-H), and a simultaneous combination of these two methods in one cell (TNT-Ag-H) were investigated. The TEM results showed that the defects formed during the electrochemical reduction, when two methods are combined, act as preferred sites for Ag nucleation, resulting in finer Ag NPs with better distribution. The average size of homogeneous distributed Ag NPs was measured in the range of 3–5 nm. Accordingly, XPS analysis showed an increased amount of Ag NPs on the surface of the modified TNTs in TNT-Ag-H sample. It was also observed that electrochemical reduction was not stable and thus had minor effects on the optical properties of the TNTs. Moreover, the TNT-Ag-H sample showed enhanced SPR and increased absorption in the whole visible light region in DRS analysis. This sample also showed a higher photocatalytic performance in the degradation of two different organic pollutants. The kinetic rate constant after 300 min reached up to 9.12 × 10-3 and 1.39 × 10-3 min−1 for MB degradation under UV and visible irradiation, respectively, which are two times higher than unmodified TNT samples.