Organic pollutant degradation for micro-molecule product emission over SiO layers-coated g-CN photocatalysts.

In this study, a SiO layer-coated g-CN catalyst was prepared by a sol-gel method to overcome the poor adsorption ability and high recombination rate of charge carriers of pristine g-CN. SEM and TEM images indicated that SiO nanoparticles were coated on the surface of g-CN nanoparticles with a layered structure and the layers were tightly contacted with g-CN. XRD patterns, FTIR spectra, UV-vis spectra and XPS spectra revealed that the structure of g-CN was not destroyed and its photoelectric catalytic properties were not suppressed by the coating of SiO layers. Adsorption experiments revealed that the SiO layers improved the adsorption performance of g-CN and their ratios were adjusted. The molecular weights of the final products of the degradation of RhB and antibiotics were at the micro-molecule level while the amount of g-CN reached 1.2% of the mass fraction, which were more suitable for pollutant degradation compared with those of g-CN due to its poor adsorption ability. The reason for this was likely that the SiO layers were not only beneficial for the adsorption of pollutants and intermediate products but also for prolonging the life time of the separated electrons and holes. Finally, active trapping experiments confirmed that both the holes and superoxide radicals were the main factors in the degradation of RhB and antibiotics, with the superoxides being the most active species.