A novel Ga(III) coordination complex as an efficient sensitizer for enhancing photocatalytic activity of TiO2/rGO nanocomposite

Abstract

Narrow solar-light response range and rapid charges recombination are the main technical barriers in TiO2 photocatalysis technology. To overcome these restrictions, in this work we synthesized a novel binuclear gadolinium (III) coordination complex, [Gd2(DPDB)6(DMF)6(H2O)2] (DPDB = [(4-dimethylamino)phenyldiazenyl] benzenesulfonate), which was used as an inorganic sensitizer for boosting the visible light-harvesting and quantum efficiency of TiO2 supported-reduced graphene oxide (rGO) nanocomposite. Crystal structure of [Gd2(DPDB)6(DMF)6(H2O)2] (Gd-CMP) was determined from single-crystal X-ray diffraction data, which indicates three-dimensional (3D) supramolecular architecture through hydrogen bonding and CH• • •𝜋ph interactions. The prepared nanohybrid (Gd-CMP/TG) reveals significantly enhanced visible-light-induced photocatalytic activity for degradation of acetaminophen (ACT). The complete removal of 10 mg/L ACT is achieved over Gd-CMP/TG, and the corresponding rate constant of ACT degradation of nanohybrid was 40‒fold higher than that of bare TiO2. In prepared ternary nanohybrid, metal-coordination sensitizer (Gd-CMP) acted as an electron donor, and at the same time, rGO served as an electron acceptor, and the synergistic effect between them efficiently enhanced charges separation and inhibited e/h pair recombination in the hybridized species. The radical scavenger tests indicated that the photo-induced O2−• radicals dominated ACT degradation. On the basis of the experimental results and calculated energy of electronic levels, a possible mechanism for the improved photocatalytic activity was discussed.