Preparation,Modification And Photocatalytic Activity Of G-C₃N₄ And G-C₃N₄/TiO₂

Photocatalysis uses solar energy as energy to remove pollutants,which is energy-saving and environmentally friendly,has a large space for development.The studies have been carried out on g-C₃N₄ and g-C₃N₄/TiO₂ modified from three aspects:morphology control,semiconductor compounding and element doping.The g-C₃N₄ was synthesized by thermal polymerization with urea,dicyandiamide and melamine,and the block g-C₃N₄ was subjected to thermal and alkali stripping.The results show that g-C₃N₄ synthesized with urea as a precursor exhibits a small layer structure;g-C₃N₄ synthesized with dicyandiamide and melamine as precursors is a block structure.The bulk g-C₃N₄ after thermal stripping forms two-dimensional nanosheet layer structure,the specific surface area increases,the band gap decreases and the separation efficiency of electrons and holes increases,which makes photocatalytic activity increased.The degree of looseness of bulk g-C₃N₄ increases after alkali stripping.Compared with the bulk g-C₃N₄,the specific surface area of g-C₃N₄ treated with 0.3 M NaOH solution increases by 4.5 times.The separation efficiency of electrons and holes increases and the efficiency of photocatalytic degradation of rhodamine B are improved.The g-C₃N₄ was added to TiO₂ sol to prepare g-C₃N₄/TiO₂?A+R?.The influence of different calcination temperatures on the performance of the catalyst was investigated.The results show that g-C₃N₄ inhibits the conversion of anatase to rutile.When the calcination is 600?,there is an optimum composite ratio between anatase and rutile,and g-C₃N₄/TiO₂?A+R?has excellent photocatalytic activity.The photocatalytic reactive groups of g-C₃N₄/TiO₂?A+R?include·OH,h⁺and·O₂^-,·O₂^-is the main.C-TiO₂?A+R?calcined at 550? by sol-gel method had the best photocatalytic performance.C-TiO₂?A+R?was mixed with g-C₃N₄?synthesized from urea?by solvent evaporation,and g-C₃N₄/C-TiO₂?A+R?photocatalyst was synthesized by calcination.The influence of the ratio of g-C₃N₄ and C-TiO₂?A+R?on the photocatalytic performance was investigated,when the mass ratio of g-C₃N₄ and C-TiO₂?A+R?is 1:10,it has better photocatalytic activity,but lower than C-TiO₂?A+R?.Figure 51,Table 6,Reference 94.