Enhanced photocatalytic performance of anatase titania nanotubes via the synergistic effect of trace copper doping and oxygen vacancies

Abstract

In this study, a trace amount of copper was successfully introduced to anatase titania nanotubes (ANTs) through a one-step solvothermal method, also generating more oxygen vacancies in the lattice. The spatial separation efficiency of the photogenerated carriers was enhanced by the synergistic effect of Cu doping and oxygen vacancies while retaining the strong redox capability of titanium dioxide. Consequently, Cu@ANTs exhibit impressive performance in degrading pollutants. Especially 0.1 wt% Cu@ANTs could remove 90% of RhB in 60 min and its performance is more than three times that of pure ANTs. The morphology and structure of the samples were analyzed comprehensively using XRD, SEM, TEM, XPS, and BET techniques. The results show that the sample has a rich porous structure and a large specific surface area. XPS analysis showed that the content of oxygen vacancies in the prepared sample increased from 13.9% to 17.87%, demonstrating the successful introduction of oxygen vacancies. The study of UV-Vis DRS, PL, and XPS valence band spectra showed that the trace amounts of copper and oxygen vacancies can regulate the band structure and facilitate the separation of photo-generated charge carriers. EPR and free radical capture experiments confirmed that ⋅OH is the main active species in the degradation of pollutants. These findings provide a reasonable explanation for the enhancement of the photocatalytic activity of Cu@ANTs and a schematic of the photocatalytic mechanism is proposed.