Effect of crystal phases of titanium dioxide on the photocatalytic activity of titanium dioxide-reduced graphene oxide composites for degradation of phenol

Titanium dioxide (TiO2) with different crystal phases generally exhibit different physical properties and photocatalytic performance. However, the effect of different phases of TiO2 on the photocatalytic activity of titanium dioxide-reduced graphene oxide (TiO2-rGO) composites prepared by photocatalytic reduction method is still unknown. In the present study, TiO2 with different phases (anatase (A), rutile (R), and mixture of anatase-rutile (A-R)) was modified with different amounts of graphene oxide (GO) loading, which were 0.5, 1, 3 and 5 wt%, via photocatalytic reduction method under 8 W UV lamp for 24 hours irradiation. The obtained composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and fluorescence spectroscopy. Transmission electron microscopy (TEM) was also used to investigate the morphology of the selected composite sample. The XRD patterns and FTIR spectra revealed that all the TiO2-rGO composite samples were successfully synthesized without disrupting the structure of TiO2. Fluorescence spectroscopy revealed the role of rGO on the TiO2-rGO composite, while TEM-EDS confirmed the presence of both TiO2 and rGO and their respective morphologies. All TiO2 samples showed good photocatalytic activity for phenol degradation under UV irradiation for 3 hours. The presence of rGO improved the activity of bare TiO2(A-R), where the enhancement observed on bare TiO2(A-R) was much higher than those on bare TiO2(A) and TiO2(R). This good improvement might be due to the presence of rGO in the composite that suppressed the electron-hole recombination of bare TiO2(A-R), as supported by the fluorescence spectra. Among all of the samples, the TiO2(A-R)-rGO composite with GO loading amount of 3 wt% showed the highest percentage degradation of phenol. The higher activity on the TiO2(A-R)-rGO composite as compared to the TiO2(A)-rGO and TiO2 (R)-rGO composites might be caused by the synergistic effect of anatase-rutile phases. This study clearly showed that the presence of rGO enhanced the activity of TiO2 and different crystal phases of TiO2 affected the photocatalytic performance of obtained TiO2-rGO composites