“…Ultimately, this leads to a shift in optical response toward the visible range. ,,, This is possible because the replacement of oxygen atoms in the TiO 2 lattice with nitrogen atoms is effective due to their similar size and relatively low ionization energy and to the stability of the Ti–N–O bonds that are formed. ,,, It is well known that photocatalytic processes involving TiO 2 are heterogeneous and that the surface area of the catalyst plays an important role. The structural properties of TiO 2 , such as its crystallinity, particle size, grain size, porosity, and surface area, are all affected by the TiO 2 synthesis method, doping method, and the type of dopant. ,,− Therefore, nanostructures based on TiO 2 nanotubes obtained by the anodic oxidation of titanium have been widely used in recent years as photocatalysts (photoanodes) due to their particular properties . Such materials are characterized by strong light-scattering effects due to their characteristic morphology, that is, densely packed tubes of a certain height that can be separated from each other. ,− In addition, highly ordered nanotubes that are vertically oriented to the metallic Ti substrate provide a high degree of electron mobility along the axis of the tubesa unidirectional charge transfer. ,, Another advantage is that it is relatively easy to control their crystalline form or degree of crystallinity (anatase, rutile, and a mixture of anatase and rutile) through temperature processes. ,,− These properties have been used effectively in various types of light-induced reactions, such as degradation of various types of dyes (methylene orange, , methylene blue, − rhodamine B, and azo dye (RB5)), pesticides (acephate), phenols, and the production of hydrogen. ,,,− Despite these advantages, a limitation in the use of nanotubes in photocatalysis as broadly understood is the nature of titanium oxide itself, and therefore its physical and chemical properties, as mentioned above.…”