Preparation of alkali metal doped g-C3N4 materials is an important branch in the research of g-C3N4 semiconductor photocatalytic materials.However,there is still lack of study on g-C3N4 materials revealing mechanisms in photosensitizer-assisted photocatalytic degradation.In this study,Na+doped g-C3N4 photocatalysts(Na+/g-C3N4)were prepared using solution synthesis,calcination,and solvothermal reaction methods.The doped position of Na+in g-C3N4 and photoelectric performance were determined.The changes of morphological,specific surface area,and pore size of Na/g-C3N4 materials were analyzed by scanning electron microscopy,N2 adsorption and desorption experiments.In Na/g-C3N4 materials,the Na+loaded in a cyclic structure composed of three heptazine structural units,coordinating with N atoms.Na/g-C3N4 changed the adsorption performance of g-C3N4,altered its bandgap width and position of conduction(valence)band,and increased its separation rate of photogenerated electrons and holes and charge transport rate of the material by affecting the 兀-conjugated system of g-C3N4.During the solvothermal reaction process for synthesis of Na+/g-C3N4,strong hydrolysis caused decomposition of unstable structures of g-C3N4 while the C-O-bonds were formed at the edge of g-C3N4.The physical and chemical adsorption sites for methylene blue(MB)of Na+/g-C3N4 materials are confirmed byπ-conjugated system and C-O-bonds of Na+/g-C3N4,by which Na+/g-C3N4 materials can adsorb MB up to 93.25％,in contrast to the g-C3N4 materials'adsorbtion only up to 24.50％.Under visible light irradiation,due to their strong adsorption capacity and photosensitivity to MB,Na+/g-C3N4 materials have constructed a unique photosensitive-photocatalytic degradation system with MB.MB not only acts as the photosensitizer for self degradation but also collaborates with Na+/g-C3N4 materials for photocatalytic degradation.At pH 6.0,the maximum degradation rate of MB is up to 96.40％in the photosensitive-photocatalytic system constructed with MB and Na+/g-C3N4 samples.
万方数据