Optimization Of The Micro/Nano Structure Of Graphitic Carbon Nitride And Enhancement Mechanism Of Visible Light Photocatalytic Removal Of Gaseous NO

With the unceasing intensification of the environmental pollution and energy shortage issues, semiconductor photocatalytic technology has a tremendous applied potential in environmental pollution remediation and energy development in an overwhelming way. Under the visible light irradiation, the utilization of graphitic carbon nitride(g-C3N4) as a photocatalyst for photocatalysis degradation of various pollutants has become challenging topics in the environmental pollution treatment field. This master dissertation focused on engineering and optimizing the micro-framework of g-C3N4 to enhance its visible light photocatalytic removal of gaseous NO by three modified approaches.The detailed modified works were shown as the following:(1) Ordered mesoporous structure of g-C3N4 was synthesized by using high surface area SiO2 and nanosphere SiO2 as two types of hard templates. These resulting materials were characterized by a series of testing. It was found that it specific surface areas and pore volumes were significantly enlarged, which can provide more active sites for photocatalytic reactions; its bandgap was increased by introducing the mesoporous structure, which can enhance its redox ability; its recombination rate of photoinduced electrons and holes was limited by incorporating the mesoporous structure, which can readily separate the photoinduced electrons and holes; its photocatalytic efficiency for gas NO removal was promoted greatly under the visible light irradiation.(2) g-C3N4 nanosheets with thin lamellar structure has been successfully obtained by thermal exfoliation, these characteristics showed that its thickness was ca. 16 nm, its specific surface areas and pore volumes can be increased to 151 m2/g, 0.52 cm3/g, respectively, all of these were much higher than bulk one of(27 m2/g,0.14 cm3/g); its bandgap was elevated by the quantum confinement effect(QCE) and enhanced redox ability of charge carriers and thus promoted the photocatalytic reactivity; in addition, the reaction intermediate of NO2 concentration during photocatalytic oxidation of NO was detected continuously, it was found that g-C3N4 nanosheets via furtherthermal treatment has improved oxidation ability.(3) A combined strategy was employed to dramatically enhance the activity of bulk g-C3N4 by simultaneously introducing mesoporous structure and hybridizing with graphene/graphene oxide, the weight ratio of G/GO to mesoporous g-C3N4 was controlled at 1.0 wt%; the pore volumes of the resultant products were increased by treatment with sonication and stirring induced the particles to re-disperse, which was beneficial to promote the mass transfer and its light harvesting capability; the bandgaps of composites were decreased by introducing the graphene materials, which can extend the light-absorption range; the recombination rate of photogenerated electrons and holes was reduced, which was improved electron transport ability and enhanced charge separation efficiency; the resulting products exhibited excellent photocatalytic activity(64.9%) after introducing the graphene materials.The original results of this study are as follows:(1) Ordered mesoporous structure of as synthesized by using high surface area SiO2 and nanosphere SiO2 as two types of hard templates, the photocatalytic reactivity and photocatalytic stability of mesoporous g-C3N4 were fully investigated.(2) g-C3N4 nanosheets with thin lamellar structure has been successfully obtained by thermal exfoliation, its enhanced reactivity for photocatalytic removal of gaseous NO was proposed.(3) Mesoporous g-C3N4/graphene and mesoporous g-C3N4/graphene oxide nanocomposites were prepared via a facile sonochemical method, their photocatalytic removal of NO can be significantly improved when introducing the weight ratio of G/GO to mesoporous g-C3N4 only at 1.0 wt%.In this paper, the experiment results presented here provide new ideas for modification of micro-structure and photocatalysis mechanism of g-C3N4, and advanced materials for the efficient photocatalytic removal of the air pollutants.