Modification And Photocatalytic Performance Of Graphitic Carbon Nitride

With constant threats related to energy shortage and environmental deterioration issues,graphitic carbon nitride?g-C₃N₄?,a novel visible-light responsive photocatalyst,has been a hot research topic.Nevertheless,bulk g-C₃N₄ suffers from such shortcomings as a small specific surface area,a high probability of photogenerated carriers recombination and low solar energy utilization efficiency,resulted in a low photoactivity.So we mainly focus on the improvement photocatalytic performanc of g-C₃N₄ by addressing the above drawbacks of pristine g-C₃N₄ in this dissertation.The achievements are as follows:1.Ultrathin graphitic carbon nitride?UGCN?nanosheets were synthesized via thermal exfoliation of bulk g-C₃N₄ under an argon atmosphere.The structure,morphology,specific surface area and photoelectric properties of the samples were characterized by the comprehensive characterization methods.The photocatalytic mechanism of UGCN was also discussed.Compared to bulk g-C₃N₄,the specific surface area of UGCN increased from 58.5 m2 g-1 to 131.2 m2 g-1,and the visible light absorption was enhanced.The kinetic rate constant of UGCN exhibits 6.1 times higher than bulk g-C₃N₄ for the degradation of RhB under visible-light irradiation.And the UGCN displayed a two-fold increase in H2 evolution.2.Plasma treatment is employed to modify the surface properties of g-C₃N₄ photocatalyst to enhance the photocatalytic performance.The comprehensive characterization methods are used to investigate the influences of plasma treatment on the surface properties.The photocatalytic mechanism of modified-g-C₃N₄ was also discussed.Compared to bulk g-C₃N₄,the surface hydrophilicity degree of modified-g-C₃N₄ increased through introducing hydrophilic-OH and-COOH groups.The degradation efficiency under visible light irradiation for the modified-g-C₃N₄ is up 2.0 times as high as that of the pristine g-C₃N₄.These findings may provide a promising and facile approach to optimize photoactivty.3.Novel g-C₃N₄/CoO composites were synthesized by one-pot calcination.The structure,morphology,specific surface area and photoelectric properties of the samples were analyzed by the comprehensive characterization methods.The photocatalytic mechanism of g-C₃N₄/CoO composites was also discussed.Experimental data verified that g-C₃N₄/CoO-0.5 wt% composites showed the highest photocatalytic activity under visible light irradiation with up to 3 times as high as that of pure g-C₃N₄.The remarkably increased photocatalytic performance of g-C₃N₄/CoO composites was mainly attributed to the matched energy band structure in g-C₃N₄/CoO heterostructure,resulting in enhanced optical absorption in visible light region and high separation rate of the photogenerated carriers.