Enhanced Photocatalytic Degradation of Methylene Blue using La3+ and Mo6+ Co-doped TiO2 Nanotubes

La 3+ single-doped and La 3+ -Mo 6+ co-doped TiO 2 nanotubes were synthesized via anodic oxidation combined with a two-step electrochemical process. Their crystalline structure, microstructure, and light absorption properties were characterized using XRD, SEM, and UV-Vis spectroscopy, followed by methylene blue photocatalytic degradation experiments. The results indicate that both La 3+ single-doping and La 3+ -Mo 6+ co-doping can suppress the transformation of the anatase phase to the rutile phase and inhibit grain growth. The diameters of both types of nanotubes range between 60-80 nm, with La and Mo uniformly distributed throughout the nanotubes. Both La 3+ single-doped and La 3+ -Mo 6+ co-doped induced red shifts in the TiO 2 light absorption peaks. The most pronounced red shift in the light absorption band edges occurred at a La 3+ -Mo 6+ ratio of 3:7, reducing the bandgap width to its minimum value of 2.99 eV. Both La 3+ single-doped and La 3+ -Mo 6+ co-doped TiO 2 exhibited first-order photocatalytic degradation of methylene blue. As the La 3+ single-doped concentration increased or the La 3+ -Mo 6+ co-doped ratio varied from 1:9 to 9:1, both the methylene blue degradation rate and photocatalytic reaction rate initially increased before decreasing, while the half-life initially decreased before increasing. At a La 3+ -Mo 6+ co-doped ratio of 3:7, the photocatalytic activity of the TiO 2 nanotubes was optimal, achieving a maximum degradation rate of 89.73% within 8 hours-a 52% improvement over pure TiO 2 nanotubes.