Ternary composites of TiO2 nanotubes with reduced graphene oxide (rGO) and meso-tetra (4-carboxyphenyl) porphyrin for enhanced visible light photocatalysis

• Nanosized H2TCPP/rGO-TNT materials are synthesized.
• H2TCPP and rGO are favorable for enhancing co-photocatalytic activity.
• A deeper insight into the co-photocatalytic mechanism is provided.
• A low cost, highly active and promising photocatalyst for future water purification devices.

Meso-tetra (4-carboxyphenyl) porphyrin (H2TCPP) loaded on the surface of TiO2 nanotubes (TNTs) by modification of reduced graphene oxide (rGO) nanostructures has been successfully performed through improved hydrothermal and heating reflux composite technology. The influence of rGO and H2TCPP on the co-photocatalytic behavior of TNT during the degradation of Methylene blue (MB) were studied. The novel photocatalysts have been characterized and analyzed by high-resolution transmission electron microscopy (TEM), elemental mapping by energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL) and electron paramagnetic resonance (EPR). The results from these investigations provide a deeper insight into the materials chemistry of H2TCPP/rGO-TNT nanocomposites. Additionally, the photocatalytic activity was evaluated by the photodegradation of MB under irradiation with visible light. The degradation results showed a purification of more than 92% MB in wastewater, which is about 4.3 times higher than that of the pure TNT. The results confirm that the prepared H2TCPP/rGO-TNT nanocomposites possess superior absorption and co-photocatalytic activities. First, graphene works as the adsorbent, electron acceptor and transporter to efficiently increase the separation of the electron–hole pairs. Then it can accelerate the decomposition of organic pollutants. Second, the H2TCPP plays a critical role in capturing photons and expands the absorption wavelength to the visible light region when dealing with water resource.