Effect of synergy between reduced graphene oxide and a Dysprosium complex on sensitization of TiO2 nanoparticles for photocatalytic degradation of atrazine under visible light

TiO2 as the most efficient advanced photocatalytic material has shown great potential for wastewater remediation. However, its efficiency is restricted due to limited visible light harvesting and low separation of carrier pairs. Herein we report a positive effect of a new mononuclear eight-coordinated lanthanide metal complex, [Dy(DMPB)3(DMF)3(H2O)2] (CFU-2) as a photosensitizer to enhance both the solar-light response and charge separation of TiO2. The prepared samples were characterized by XRD, BET, FT-IR, Raman, UV–Vis diffuse reflectance, cyclic voltammetry, and electrochemical impedance spectroscopy. Mott-Schottky plots were also used to investigate the band-edge potentials of the samples, which revealed a suitable LUMO energy level of CFU-2 for effective electron injection to the conduction band of TiO2. The optimized photocatalyst indicated an improved photocatalytic activity under visible light irradiation for photo-oxidation of atrazine (ATZ). The addition of 1.5 mM CFU-2 increased the rates of ATZ oxidation 32‒fold higher than that of pure TiO2. Moreover, the deposition of the catalyst on the surface of reduced graphene oxide (RGO) provided a high surface area, and further reduced the rate of electron-hole recombination. In this architecture, CFU-2 and RGO acted as electron donor and electron acceptor, respectively. Accordingly, the synergistic effects of visible light harvesting of CFU-2, the intimate contact between the TiO2, RGO, and CFU-2, and the accelerated electron transfer led to the high photocatalytic performance of the CFU-2@TiO2/RGO.