Synthesis Of Graphitic Carbon Nitride-Based Composite Materials For Photocatalytic Hydrogen Evolution

Graphite carbon nitride,as a metal-free photocatalyst,has attracted extensive attention in the field of photocatalytic energy conversion.In this paper,a series of composites based on g-C3N4 have been successfully prepared by different methods.The experimental results show that the photocatalytic performance of the composite material has been significantly enhanced.The research contents are as follows:(1)In this paper,Ag-based g-C3N4 composites have been successfully fabricated through two deferent synthetic methods:a facile and effificient precipitationcalcination strategy(denoted as D-CN-xAg,x represents the dosage of Ag2CO3,the same below),a calcination method(denoted as Z-CN-xAg).We also found that the photocatalytic performance of the composite material D-CN-5%Ag is the best,and the corresponding hydrogen production is 153.33 μmol g-1 h-1,which is 4.6 times higher than that of Z-CN-5%Ag composite.This might be attributed to appropriate content of metallic Ag and more active sites exposed on the surface of D-CN-5%Ag composite.Meanwhile,combining with photoelectrochemical results,it could be inferred that LSPR effect and the intimate interfacial between metallic Ag and g-C3N4 in the system play also important role for promoting the separation and transmission of photoelectric charge the improvement of photocatalytic activity.(2)CdS/Ag2S/g-C3N4 ternary composite photocatalysts with different amounts of Ag2S were successfully synthesized through simple chemical deposition method.These photocatalysts were characterized by XRD,FTIR.SEM,EDX mapping and XPS to analyze the information of structure and composition.As photocatalysts,the optimal component ratio of composite photocatalysts with superior photocatalytic performance had been investigated.Among these photocatalysts,CdS/Ag2S2%/g-C3N4 ternary composite photocatalyst possessed the best photocatalytic activity toward H2 production from water,about 1020.54 μmol g-1 h-1 in Na2S-Na2SO3 solution.Furthermore,based on the photoelectrochemical results,the improved photocatalytic activity could not only be attributed to the synergic effect of ternary component in the composite,but could also be caused by Ag2S that offered abundant active sites for H2 production.