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

Graphitic carbon nitride (g-CN) has attracted growing attention recently for photodegradation of pollutants. However, the photosensitization performance of g-CN was limited by insufficient generation efficiency of reactive oxygen species (ROS) and weak light absorption. In this study, platinum (Pt)-doped g-CN photocatalyst was synthesized by thermal polycondensation using dicyandiamide and chloroplatinic acid. The structure and composition of Pt-doped g-CN 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-CN was successfully prepared. Compared with bare g-CN, Pt-doped g-CN 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 Pt-doped g-CN, while photodegradation efficiency for Rhodamine B (RhB) increased from 50 to 90%. The effecting factors of adsorption and photocatalytic degradation performance of Pt-doped g-CN 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 Pt-doped g-CN were generated. The electrons reacting with dissolved oxygen produce active oxygen species such as •OH and O, which can degrade RhB on the surface of Pt-doped g-CN. 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.