Study On Hydrolysis Of Water By Functionalized Two-Dimensional Graphitic Carbon Nitride And Graphene Composite Photocatalyst

Since 1970s,photocatalytic technology has become one of the effective ways to solve energy and environmental problems due to the ability to convert sunlight into chemical energy,degradation of pollutants,decomposition of water to hydrogen and oxygen production.Graphitic carbon nitride(GCN)as a new visible light response photocatalyst,has a unique two-dimensional structure,excellent chemical stability and adjustable electronic structure.A single GCN has a high photogenerated electron and hole recombination rate,its quantum efficiency is low,and affecting its photocatalytic activity.In this paper,the deficiency of GCN was studied by using acid water treatment and concentrated heat-precipitation treatment to improve the specific surface area and increase the active sites.The GCN based catalyst were formed with two-dimensional graphene oxide and the functionalized GCN by self-assembly.Then,GO is reduced to rGO,thereby reducing the recombination efficiency of photogenerated carriers and improving the photocatalytic activity.The main research contents are as follows:1,Functionalization of GCN(1)The porous protonated GCN(pGCN)was prepared by HNO3 and H2SO4 acid treatment and hydrothermal treatment.Compared with GCN,the surface area of the active site exposed to more active sites,the surface area also increased significantly to 82.76 m2g-1.The band gap is 2.91 eV,which can much better respond to visible light.Besides,the protonated surface is conducive to photogenerated carriers in its surface transmission.The photocatalytic activity of pGCN was significantly better than that of GCN.(2)The GCN/H2SO4 solutions was obtained by stirring the mixture of GCN and H2SO4 with constant temperature condensing reflux method.Since H2O was a poor solvent for GCN but dissolvable in H2SO4,precipitated GCN(PCN)was prepared by adding H2O into the GCN/H2SO4 solution.The structure,composition,morphology and optical properties of the samples were characterized by XRD,XPS,FTIR,SEM,UV-Vis,DRS and PL.After dissolving and re-precipitating,GCN is thinner than GCN,and S element and proton are introduced to increase its active sites,promote the separation of photogenerated carriers and improve the photocatalytic activity.2?GCN-rGO photocatalyst reduce the recombination efficiency of photogenerated carriers(1)The pGCN-rGO composite photocatalyst was prepared by electrostatic self-assembly and microwave-assisted reduction.The treated positively charged pGCN favors the interaction with the negatively charged GO to be more closely integrated.It can be seen from the optical properties that the visible light absorption of pGCN-rGO is significantly enhanced and the PL intensity is significantly reduced,indicating better light absorption and lower charge recombination rate.In addition,the pGCN-5wt%rGO superhybrid demonstrates superior photocatalytic degradation activity under visible light,which presents 99.4%degradation efficiency after 80 min and presents the superb photocatalytic reduction capacity and reaches the yields of 557 ?molg-1h-1 for H2.(2)PCN-GO was prepared by adding GO dispersions into the GCN/H2SO4 solution self-assembly.The PCN-rGO composite photocatalyst with stable performance was prepared by photoreduction.Due to its special precipitation and self-assembly function,PCN-rGO composite promote the separation of photogenerated carriers.In addition,reduced graphene can enhance the visible light utilization of materials and promote electron transfer.The photocatalytic activity of PCN-rGO composite have greatly improved than before.The PCN-2wt%rGO superhybrid reaches the yields of 715 ?mol g-1h-1for H2.