Synthesis, electron transfer and photocatalytic activity of TiO2 nanotubes sensitized by meso-tetra(4-carboxyphenyl)porphyrin under visible-light irradiation

TiO2 plays a crucial role in the materials field due to its excellent chemical and physical properties. However, the TiO2 band edge is located in the UV region, which makes this species inactive under visible light irradiation. Porphyrins have drawn a great deal of attention as sensitizers due to the large absorption coefficients of their Soret and Q bands in the visible region. Here, we applied a new strategy using TiO2 nanotubes sensitized by meso-tetra(4-carboxyphenyl) porphyrin (H2TCPP) to broaden the absorption spectra to fill the valley between the Soret and Q bands. With this novel approach, TEM, DRS, XRD and XPS were employed to confirm that the TiO2 nanotubes were successfully sensitized by the H2TCPP, EPR and PL emission spectra showed that excited electrons transfer more effectively, and the photo-generated electron-hole pairs separated more effectively under visible light irradiation. Therefore, TiO2 nanotubes sensitized by H2TCPP can be used to increase the photo-generated electron activity when used as a visible-light photocatalyst under visible light irradiation.