The synergy of adsorption and photosensitization of platinum-doped graphitic carbon nitride for improved removal of rhodamine B

Graphitic carbon nitride (g-C3N4) has attracted growing attention recently for photodegradation of pollutants. However, the photosensitization performance of g-C3N4 was limited by insufficient generation efficiency of reactive oxygen species (ROS) and weak light absorption. In this study, platinum (Pt)–doped g-C3N4 photocatalyst was synthesized by thermal polycondensation using dicyandiamide and chloroplatinic acid. The structure and composition of Pt-doped g-C3N4 were tested by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-mass spectrometry (ICP-MS), which indicated that the Pt-doped g-C3N4 was successfully prepared. Compared with bare g-C3N4, Pt2+-doped g-C3N4 has wider light absorption range, lower band gap, and higher photon-generated carrier migration efficiency, which significantly improved the light absorption range and photosensitization efficiency of Pt2+-doped g-C3N4, while photodegradation efficiency for Rhodamine B (RhB) increased from 50 to 90%. The effecting factors of adsorption and photocatalytic degradation performance of Pt2+-doped g-C3N4 for RhB were investigated in detail. The adsorption is a monolayer adsorption process that fits the Langmuir model, as well as being a spontaneous endothermic process. Using a white LED as an excitation source, electrons and holes in Pt2+-doped g-C3N4 were generated. The electrons reacting with dissolved oxygen produce active oxygen species such as •OH and 1O2, which can degrade RhB on the surface of Pt2+-doped g-C3N4. The photocatalytic method has the advantages of simple operation, low cost, and high efficiency, and has the potential to directly remove dyes in wastewater utilizing sunlight.