Preparation And Properties Of Iodine-doped Carbon Nitride/Graphene/Titanium Dioxide Photocatalysis

The shortage of traditional energy resources has become increasingly serious on the burgeoning society.What’s worse,the massive usage of traditional energy sources has led to a negative influence to the environment in which we live.Solar energy,as the most ideal green energy,has always been an important theme for the research workers.Semiconductor photocatalytic technology has attracted worldwide attention because of its function to convert solar energy into chemical energy under mild conditions,and to decompose organic pollution.Recent years,graphitic carbon nitride（g-C₃N₄）has become the hot topic in the field of photocatalysis research due to its unique electronic structure and excellent thermal stability and chemical stability.In this paper,the g-C₃N₄ photocatalyst was prepared by thermal poly-condensation with melamine as the precursor,and a series of modification methods were used to reduce the recombination of the photo-generated electrons and holes and to improve the visible light utilization efficiency.（1）Firstly,solvothermal method was used to fabricate g-C₃N₄/TiO₂heterojunction system and the TiO₂/CN-0.50 represented the highest photocatalytic efficiency because of the optimal addition amount of TiO₂.Secondly,the iodine doped graphitic carbon nitride was used to increase the light absorption capacity,and the CNI_1.0 put up the best photocatalytic activity.Finally,iodine doped carbon nitride/titanium dioxide composite heterojunction system TiO₂/CNI_1.0 was prepared by combining the two modification methods.The results showed that the rate of hydrogen production of TiO₂/CN-0.50 was increased to 2.9 times than that of bulk carbon nitride with 3wt%Pt loading（co-catalyst）and 20%triethanolamine（sacrificial reagent）and under visible light（λ≥420 nm）.The analysis shows that iodine doped carbon nitride could broaden the visible light absorption range,and the construction of heterojunctions could realize the spatial separation of photo-generated electrons and holes.Thus,the combination of doping and heterojunction methods enabled the catalytic activity of g-C₃N₄ to be further improved.（2）Melamine was chosen as the precursor and graphene oxide as addictive to prepare g-C₃N₄,by changing the amount of graphene oxide,and the CN/rGO-2.50exhibited the best performance.On the basis of the heterojunction,graphene oxide was introduced to enhance the contact between the graphitic carbon nitride and the titanium dioxide particles,and two kinds of ternary composite catalysts TiO₂/rGO/CNI_1.0 and TiO₂/rGO/CNI were prepared.Under visible light（λ≥420 nm）and 3wt%Pt loading and 20%triethanolamine,the efficiency of splitting water were TiO₂/rGO/CNI_1.0(540.1μmol·g^-1·h^-1)>TiO₂/rGO/CN(413.0μmol·g^-1·h^-1)>TiO₂/CNI_1.0(327.0μmol·g^-1·h^-1)>TiO₂/CN-0.50(275.3μmol·g^-1·h^-1)>g-C₃N₄(109.7μmol·g^-1·h^-1)。Among them,the rate of hydrogen production of the ternary composite TiO₂/rGO/CNI_1.0 increased to 4.9 times than that of the bulk carbon nitride（g-C₃N₄）.The analysis shows that the transmission capacity of photo-generated electrons from the graphitic carbon nitride materials to the titanium dioxide particles increased due to the introduction of graphene.Thereby the recombination of photo-generated electrons and holes were further reduced,and so,the photocatalytic activity of the graphite carbon nitride material was increased.