Microstructure and crystallographic properties are discussed in detail in . Briefly, X-ray powder diffraction (XRPD) analyses showed that copper ions did not enter TiO2 structure. However, together with graphene, they hindered the anatase-to-rutile phase transition (ART), and the nucleation and growth of both anatase and rutile crystalline domains . Indeed, we previously showed that unmodified TiO2 thermally treated at 250 °C / 8h consisted of 92.8 wt% anatase, 5.1 wt% rutile, and 2.1 wt% brookite. Anatase fraction increased to 94.4 wt%, and 95.5 wt% in Cu-G0.5/250, and Cu-G1.0/250, respectively. Anatase crystalline domains in unmodified TiO2 were shown to have an average diameter of 4.4 nm, those of rutile 8.7 nm. The addition of copper and graphene led to a smaller size of anatase's domains, being around 3 nm in Cu-G0.5/250, and Cu-G1.0/250, respectively.