Structure phase-dependent dielectric and photodegradation properties of Co-doped TiO2 nanoparticles synthesized via co-precipitation route

This research pursued the effect of various calcination temperatures (300–1000 °C) on developing structural phases and the optical, dielectric, and photodegradation characteristics of cobalt-doped titanium dioxide nanoparticles (TiO2 NPs). The prepared NPs were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared (FTIR) spectroscopy analysis, ultraviolet–visible light (UV–VIS) spectroscopy, and photodegradation of methylene blue in the presence of visible light. XRD analysis revealed the formation of a tetragonal anatase phase for the samples calcined at 300–600 °C, while the Co-doped samples calcined at 800 °C and 1000 °C displayed a tetragonal rutile phase. The optical band gap analysis indicated that doping in the host matrix produced lower band gap energy for all the prepared samples. Dielectric measurements showed that the rutile phase heated at 800 °C had a larger dielectric constant and dielectric loss than the un-doped TiO2 and the other cobalt-doped samples. Finally, the anatase Co-doped TiO2 exhibited a maximum MB degradation of 93 % in 90 min compared to un-doped TiO2, which only degraded 14 % and rutile-TiO2 NPs (62 % degradation). The underlying mechanism responsible for the diverse photodegradation performance displayed by the anatase and rutile phases of TiO2 NPs is discussed. Overall, these results demonstrate that cobalt doping and the crystalline phase of TiO2 NPs are vital parameters involved in optimizing the photocatalytic activity of TiO2.